Positive type photoresist composition

ABSTRACT

A positive type photoresist composition suitable for light in the wavelength region of 170 nm to 220 nm, high in sensitivity, excellent in adhesion and giving a good resist pattern profile, which comprises a resin having an ester group represented by the following general formula [I] in its molecule and a compound generating an acid by irradiation of an active light ray or radiation: 
                         
wherein R 1  represents a hydrogen atom, an alkyl group or a cycloalkyl group; and R 2  and R 3 , which may be the same or different, each represents a hydrogen atom, an alkyl group, a cycloalkyl group or -A-R 4 , and R 2  and R 3  may combine together to form a ring, wherein R 4  represents a hydrogen atom, an alkyl group or a cycloalkyl group, R 4  and R 2  or R 3  may combine together to form a ring, and A represents an oxygen atom or a sulfur atom.

This is a continuation of application Ser. No. 09/023,801 filed Feb. 12,1998, the disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a positive type photoresist compositionsuitable for exposure treatment with active light rays or radiation,particularly light rays having a wavelength as very short as 170 nm to220 nm, and more particularly to a positive type photoresist compositionhigh in sensitivity, and giving an excellent resist pattern and apattern excellent in adhesion to a substrate.

Further, the present invention relates to an ultramicro-lithographyprocess or another photo-fabrication process for producing a very largescale integrated circuit or a high capacity microchip, and moreparticularly to a positive type photoresist composition which can form ahighly refined pattern by use of far ultraviolet rays including excimerlaser beams.

BACKGROUND OF THE INVENTION

In recent years, there have been glowing demands in the field ofproduction of various electronic devices requiring fine processing suchas semiconductor elements towards the devices progressively increased indensity and integration. This makes very severe the requiredperformances for the photography techniques for realizing refinedpatterns. Contributing to this refining technique are photoresistsincreased in resolution and exposure light having a shortenedwavelength.

In general, the resolution (Res) of the optical system can berepresented by the Rayleigh equation, namely Res=κ·λ/NA (wherein κ is aprocess factor, λ is a wavelength of an exposure light source, and NA isthe number of openings of a lens). This equation shows that the width ofa reproduced line can be decreased to resolve a fine pattern (namelyhigh resolution can be obtained) by shortening the wavelength at thetime of exposure. Surely, the exposure wavelength has been sifted to theg-line (436 nm) and the i-line (365 nm) of a high pressure mercury lampwith a decrease in the minimum width of the reproduced line, and theproduction of the devices by use of the KrF excimer laser beam (249 nm)has been studied. For further fine processing, the use of an excimerlaser beam having a shorter wavelength, particularly ArF (193 nm), has agood prospect.

Looking at photoresists exposed to shortwave light, high integration inmultilayer resist systems utilizing surface lithography, not inmonolayer resist systems which have previously been used in theindustrial production, is also studied. However, it still suffers fromthe problem of complicated processes which have prevented the practicalapplication of the multilayer resists.

In the case of excimer lasers including KrF excimer lasers, it isgenerally considered that the life of gases is short, and that the costperformance of the lasers is required to be improved because exposuredevices themselves are expensive.

Responding to this are so-called chemical amplification type resistsbecoming the main current in KrF excimer laser exposure applications. Inthe chemical amplification type resists, acids are generated from photoacid generators existing in catalytic amounts in the systems byexposure, and protective groups of alkali-soluble groups of binders orlow molecular weight compounds are eliminated with the catalytic amountof acids by the catalytic reaction to ensure discrimination of thesolubility in alkali developing solutions. In the chemical amplificationtype resists, the acids generated by the photocatalytic reaction arecatalytically utilized, so that an increase in sensitivity is expected.

In general, the chemical amplification system resists can be roughlydivided into three classes, commonly called as a 2-component system, a2.5-component system and a 3-component system. In the 2-componentsystem, a photo acid generator is combined with a binder resin. Thebinder resin is a resin having a group which is decomposed by the actionof an acid to enhance the solubility of the resin in an alkalideveloping solution (which is also referred to as an acid decomposablegroup) in its molecule. The 2.5-component system contains a lowmolecular weight compound further having an acid decomposable group inaddition to such a 2-component system. The 3-component system containsthe photo acid generator, the alkali-soluble resin and theabove-mentioned low molecular weight compound.

However, when the wavelength of exposure light becomes short, a newproblem is encountered. That is, in the photoresists, raw materials goodin transparency to shortwave light is poor in resistance to dry etching.On the other hand, there is the problem that raw materials good inresistance to dry etching is poor in transparency. The compatibility ofthe resistance to dry etching and the transparency is basically theproblem of the performance of the binder resins contained in photoresistlayers.

The binder resins include novolak resins and poly(p-hydroxystyrene). Thenovolak resins are widely utilized as alkali-soluble resins for i-lineresists, and the poly(p-hydroxystyrene) resins are used as base polymersfor KrF excimer laser resists. These produce no problem as long aslong-wave light is used. However, different therefrom, the use ofshortwave light rises a problem. In particular, the above-mentionedresins have high optical density within the wavelength region of 170 nmto 220 nm. It is therefore actually difficult to directly use theseresins as with the conventional methods. Accordingly, the development ofresins high in light transparency and resistance to dry etching has beenlooked forward to.

One of the general solutions to this problem is a method of introducing,for example, an alicyclic hydrocarbon moiety into the resin. There isalso a method of utilizing a naphthalene skeleton, one of the aromaticcompounds. In particular, various reports disclose that the introductionof alicyclic hydrocarbon moieties fulfills demands for both lighttransparency and resistance to dry etching. For example, it is describedin Journal of Photopolymer Science and Technology, 3, 439 (1992).

On the other hand, what to select as the acid decomposable groupcontained in the resin is important, particularly, because it affectsthe sensitivity and resolution of the resist and further the agingstability.

The acid decomposable groups for protecting carboxylic acid groups,which have hitherto been mainly reported, include tertiary alkyl esterssuch as t-butyl esters and acetal esters such as tetrahydropyranylesters and ethoxyethyl esters. However, the t-butyl ester groups havethe drawback that the ability of being eliminated with the generatedacids is low, resulting in a lowering of the sensitivity. Conversely,the tetrahydropyranyl esters and the ethoxyethyl esters have a largeproblem with the aging stability because of their easy decomposition atordinary temperatures.

Further, JP-A-5-346668 (the term “JP-A” as used herein means an“unexamined published Japanese patent application”) has proposed to use3-oxocyclohexyl ester groups as the acid decomposable groups. However,they are not necessarily satisfactory in sensitivity.

As described above, for the acid decomposable groups for protecting thecarboxylic acids which satisfy the sensitivity and the aging stabilityof the photoresists at the same time, how to design the aciddecomposable groups has been not necessarily clear.

Furthermore, in order to decrease the width of the reproduced line toresolve the fine pattern in the resulting resist pattern, not only theabove-mentioned characteristics but also sufficient adhesion of the finepattern obtained to a substrate is required. Even if the fine pattern isobtained, insufficient adhesion thereof sometimes causes separationthereof.

On the other hand, in photofabrication processes of lithography, theproduction of semiconductors for ICs and the production of circuitsubstrates for thermal heads, semiconductor wafer, glass, ceramic ormetal substrates are coated with photoresists to a thickness of 0.5 μmto 2.5 μm by spin coating or roller coating, followed by heating anddrying. Then, circuit patterns are printed thereon through exposuremasks with active light such as ultraviolet rays, and baked afterexposure if necessary, followed by development to form images of theresists. Further, pattern processing can be performed on the substratesby etching using the images as masks.

In many cases, alkali-soluble resins and photosensitive materials aregenerally used in combination as positive type photoresist compositions,and especially, compositions comprising novolak type phenol resins andnaphthoquinone-diazide compounds in combination are used. The positivetype photoresists comprising the novolak resins and quinonediazidecompounds have advantageous characteristics such as high resistance toplasma etching, the prevention of dissolution of thenaphthoquinonediazide compounds, the disappearance of the ability ofpreventing the compounds from being dissolved, associated withcarboxylic acids by light irradiation, and an improvement in alkalisolubility of the novolak resins as a result thereof. Accordingly, anumber of the photoresists have been developed and have come inpractice, and sufficient results have been obtained for processing of aline width up to about 0.8 μm to about 2 μm.

However, integrated circuits have been progressively increased in theirintegration degree, and therefore processing of ultrafine patternshaving a line width of a half micron or less has become necessary in theproduction of semiconductor substrates for very large scale integratedcircuits. For fulfilling this necessity, the wavelength of light used inexposure devices employed for photolithography becomes progressivelyshorter, and now, of the far ultraviolet rays, the use of excimer laserlight having a short wavelength (such as XeCl, KrF or ArF) has beenstudied.

In the pattern formation of lithography in this wavelength region, theabsorption of the novolak resins and the naphthoquinonediazide compoundsin the far ultraviolet region is so strong that light becomes difficultto arrive at the bottom portions of the resists. Accordingly, onlypatterns low in sensitivity and tapered are obtained. Thenovolak-naphthoquinonediazide resists are therefore insufficient.

One means for solving this problem is chemical amplification systemresist compositions described in U.S. Pat. No. 4,491,628 and EuropeanPatent 249,139. The positive type chemical amplification system resistcomposition is a composition designed so as to produce an acid in anexposed area by irradiation of active light such as far ultraviolet raysand to change the solubility of the area irradiated with active lightand an area not irradiated therewith in a developing solution by areaction using this acid as a catalyst, thereby forming a pattern on asubstrate.

Examples of such resins which are used in combination with the photoacid generators and changed in solubility with the acids include acetalor O,N-acetal compounds (JP-A-48-89003), orthoesters or amidoacetalcompounds (JP-A-51-120714), polymers having acetal or ketal groups onmain chains (JP-A-53-133429), enol ether compounds (JP-A-55-12995),N-acyliminocarboxylic acid compounds (JP-A-55-126236), polymers havingorthoecter groups on main chains (JP-A-56-17345), tertiary alkyl estercompounds (JP-A-60-3625), silyl ester compounds (JP-A-60-10247) andsilyl ether compounds (JP-A-60-37549 and JP-A-60-121446). Thesecompounds exceed 1 in quantum yield in principle, so that they exhibithigh photosensitivity.

Similarly, the systems which are stable at room temperature, but aredecomposed in the presence of acids by heating to be solubilized inalkalis include, for example, combined systems of photo acid generatorsdescribed in JP-A-59-45439, JP-A-60-3625, JP-A-62-229242, JP-A-63-27829,JP-A-63-36240 JP-A-63-250642, Polym. Eng. Sci., 23, 1012 (1983), ACS.Sym., 242, 11 (1984), Semiconductor World, November, 91 (1987),Macromolecules, 21, 1475 (1988) and SPIE, 920, 42 (1988), and esters oftertiary or secondary carbon (for example, t-butyl or 2-cyclohexenyl) orcarbonic ester compounds. These systems also have high sensitivity andcan be effective for the above-mentioned shortening of the wavelength oflight sources, because of their lower absorption in the far ultravioletregion, compared with the novolak resin/naphthoquinonediazide systems.

In particular, there are proposed resist compounds comprisinghydroxystyrene polymers particularly low in photoabsorption when the248-nm light of a KrF excimer laser is used, into which acetal groups orketal groups are introduced as protective groups. Examples thereof aredescribed in JP-A-2-141636, JP-A-2-19847, JP-A-4-219757 andJP-A-5-281745. Besides, similar compositions having t-butoxycarbonyloxygroups or p-tetrahydropyranyloxy groups as acid decomposable groups areproposed in JP-A-2-209977, JP-A-3-206458 and JP-A-2-19847. However,these compositions substantially have the disadvantage of lowsensitivity caused by too high absorbance when an ArF laser is used as alight source. Accompanied thereby, they further have the problems ofdeterioration of pattern profiles and lack of focus permissibility, sothat many improvements are required.

As the photoresist compositions for the ArF light source, photoresistcompositions in which (meth)acrylic resins smaller in absorption thanpartially hydrogenated hydroxystyrene resins are combined with compoundsgenerating acids with light are proposed, for example, in JP-A-7-199467and JP-A-7-252324. Above all, JP-A-6-289615 discloses resins in whichorganic groups of tertiary carbon are attached by ester linkages tooxygen of a carboxyl group of acrylic acid, and JP-A-7-234511 disclosescopolymer resins comprising structural units in whichdimethyl-substituted tertiary carbon groups are attached by esterlinkages to oxygen of a carboxyl group of acrylic acid, and structuralunits in which alicyclic groups are attached by ester linkages. Theseresins have photoabsorptive aryl groups in carbon substituent groups, orare poor in acid decomposability although improved in light permeabilityto the ArP light source. Thus, resins exhibiting characteristicssufficiently satisfactory to the object have not been obtained yet.

Here, also with respect to the photo acid generators used in thepositive type chemical amplification resists as described above, theprior art is described. The known photo acid generators includeN-imidosulfonates, N-oximesulfonates, o-nitrobenzylsulfonates andpyrogallol trimethanesulfonate. Further, as the agents high inphotolysis efficiency and excellent in image forming properties,sulfoniums and iodoniums are known. As counter bases thereto, perfluoroLewis acid bases such as PF₆ ⁻, AsF₆ ⁻ and SbF₆ ⁻, and further atrifluoromethanesulfonic acid anion and a toluenesulfonic acid anion areknown. Furthermore, from the viewpoint of improving solvent solubility,benzene-sulfonic acid, naphthalenesulfonic acid and anthracene-sulfonicacid each having one straight-chain alkyl group or alkoxyl group arealso disclosed. However, all of them are not sufficiently overcome indrawbacks such as contamination with counter anion elements and thinningof resist patterns with time from exposure to heating treatment, andmore improvements in sensitivity and resolution are desired.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a positivetype photoresist composition sufficiently suitable for light,particularly, within the wavelength region of 170 nm to 220 nm, highlysensitive to light, excellent in a resist pattern profile obtained, andexcellent in adhesion to a substrate.

Another object of the present invention is to solve the problems oftechniques improving the essential performance of the above-mentionedmicrophotofabrication using far ultraviolet rays, particularly excimerlaser beams, namely to develop a resist composition satisfying requiredcharacteristics such as sensitivity, resolution and a pattern profile tothe use of the shortwave light sources. Of these, a primary object ofthe present invention is to develop a photoresist compositionparticularly low in absorbance to an ArF excimer laser light source,therefore high in sensitivity, and accompanied thereby, also excellentin resolution and a pattern profile.

A further object of the present invention is to develop a photoresistcomposition having an acid decomposable group to which theabove-mentioned tertiary carbon atom is attached by an ester linkage,which is improved in the prior-art disadvantages, namely low inabsorbance and good in acid decomposability, therefore high insensitivity, good in a pattern profile and excellent in storagestability, to an ArF excimer laser light source.

As a result of intensive studies in view of the above-mentioned variouscharacteristics, the present inventors have discovered that the objectsof the present invention can be successfully attained by using a resincomprising a group having a specific structure, thus completing thepresent invention.

Further, the present inventors have intensively studied materialsconstituting resist compositions in positive type chemical amplificationsystems. As a result, the present inventors have known that the objectscan be attained by a combination of a (meth)acrylic resin containingstructural units each having an acid decomposable substituent group of aspecific structure and a photo acid generator, thus completing thepresent invention.

That is, the above-mentioned objects can be attained by the followingconstitution:

(1) A positive type photoresist composition comprising a resin having anester group represented by the following general formula [I] in itsmolecule and a compound generating an acid by irradiation of an activelight ray or radiation:

wherein R₁ represents a hydrogen atom, an alkyl group or a cycloalkylgroup; and R₂ and R₃, which may be the same or different, eachrepresents a hydrogen atom, an alkyl group, a cycloalkyl group or -A-R₄,and R₂ and R₃ may combine together to form a ring, wherein R₄ representsa hydrogen atom, an alkyl group or a cycloalkyl group, R₄ and R₂ or R₃may combine together to form a ring, and A represents an oxygen atom ora sulfur atom.

(2) The positive type photoresist composition described in the above(1), wherein said resin is a resin containing repeating structural unitsrepresented by the following general formula [II]:

wherein R₁ to R₄ have the same meanings as given in the above (1); R₅represents a hydrogen atom or a methyl group; and X represents one groupselected from the group consisting of a single bond, an alkylene group,a substituted alkylene group, an ether group, a thioether group, acarbonyl group, an ester group, an amido group, a sulfonamido group, aurethane group and a urea group, or a combination of two or more ofthem.

(3) The positive type photoresist composition described in the above (1)or (2), wherein said resin further contains repeating structural unitseach having an alicyclic hydrocarbon moiety.

(4) The positive type photoresist composition described in the above(3), wherein said repeating structural units each having a alicyclichydrocarbon moiety are repeating structural units represented by thefollowing general formula [III]:

wherein R₅ has the same meaning as given in the above (2); and R₆represents a monovalent alicyclic hydrocarbon group.

(5) The positive type photoresist composition described in the above(3), wherein said repeating structural units each having a alicyclichydrocarbon moiety are repeating structural units represented by thefollowing general formula [IV]:

wherein R₅ has the same meaning as given in the above (2); and R₇represents a connecting group containing a divalent alicyclichydrocarbon moiety; and G represents —COOH, —OH, —COOR₈ or —OR₈ whereinR₈ represents a tertiary alkyl group, a tetrahydropyranyl group, atetrahydrofuranyl group, —CH₂OR₉ or —CH(CH₃)OR₉ wherein R₉ represents analkyl group.

(6) A positive type photoresist composition comprising a resin which hasan ester group represented by the following general formula [I-2] in itsmolecule and is decomposed by action of an acid to increase solubilityin an alkali solution, and a compound generating an acid by irradiationof an active light ray or radiation:

wherein R₂₁ to R₂₄, which may be the same or different, each representsa hydrogen atom or an alkyl group; and m represents 1 or 2.

(7) The positive type photoresist composition described in the above(6), wherein said resin is a resin which contains repeating structuralunits corresponding to a monomer represented by the following generalformula [II-2] and is decomposed by action of an acid to increasesolubility in an alkali solution:

wherein R₂₁ to R₂₄ and m have the same meanings as given in the above(6); R₂₅ represents a hydrogen atom or a methyl group; and A₂₁represents one group selected from the group consisting of a singlebond, an alkylene group, a substituted alkylene group, an ether group, athioether group, a carbonyl group, an ester group, an amido group, asulfonamido group, a urethane group and a urea group, or a combinationof two or more of them.

(8) The positive type photoresist composition described in the above (6)or (7), wherein said resin further contains repeating structural unitseach having an alicyclic hydrocarbon moiety.

(9) The positive type photoresist composition described in any one ofthe above (6) to (8), wherein said resin further contains repeatingstructural units each having a group which is decomposed by action of anacid to increase solubility in an alkali developing solution.

(10) A positive type photoresist composition for far ultraviolet rayexposure comprising a resin which is decomposed by action of an acid toincrease solubility in an alkali solution, and a compound generating anacid by irradiation of an active light ray or radiation, wherein saidresin is a polymer containing a monomer represented by the followinggeneral formula [I-3] as one of repeating structural units:

wherein R₃₁ represents a hydrogen atom or a methyl group; R₃₂ to R₃₄,which may be the same or different, each represents a hydrogen atom oran alkyl group; R₃₅ and R₃₆, which may be the same or different, eachrepresents a hydrogen atom, an alkyl group or X₃₁R₃₇ wherein R₃₇ is ahydrogen atom or an alkyl group, and X₃₁ is an oxygen atom or a sulfuratom; A₃₁ represents one group selected from the group consisting of asingle bond, an alkylene group, a substituted alkylene group, an ethergroup, an ester group, a thioether group, a carbonyl group, an amidogroup, a sulfonamido group, a urethane group and a urea group, or acombination of two or more of them; and m′ is 1, 2 or 3, n′ is 0, 1 or2, and the sum of m′ and n′ is 3.

(11) The positive type photoresist composition described in the above(10), wherein said resin is a copolymer containing repeating units of amonomer represented by general formula [I-3] and a monomer having analicyclic hydrocarbon moiety in its molecule.

(12) The positive type photoresist composition described in the above(10) or (11), wherein the active light ray or the radiation for exposurehas a wavelength of 170 nm to 220 nm.

(13) The positive type photoresist composition described in the above(10) or (11), wherein said resin further contains repeating structuralunits each having a group which is decomposed by action of an acid toincrease solubility in an alkali developing solution.

(14) The positive type photoresist composition described in any one ofthe above (10) to (12), wherein said composition is composed so as togive a transmission optical density of 1.0 or less per micron of coatedlayer in thickness to an active light ray having a wavelength of 193 nm.

(15) A positive type photoresist composition for far ultraviolet rayexposure comprising a resin which is decomposed by action of an acid toincrease solubility in an alkali solution, and a compound generating anacid by irradiation of an active light ray or radiation, wherein saidresin is a polymer containing a monomer represented by the followinggeneral formula [I-4] as one of repeating structural units:

wherein R₄₁ represents a hydrogen atom or a methyl group; R₄₂ to R₄₄,which may be the same or different, each represents a hydrogen atom oran alkyl group; R₄₅ and R₄₆, which may be the same or different, eachrepresents a hydrogen atom, an alkyl group or a halogen atom; X₄₁represents a halogen atom; A₄₁ represents one group selected from thegroup consisting of a single bond, an alkylene group, a substitutedalkylene group, an ether group, an ester group, a thioether group, acarbonyl group, an amido group, a sulfonamido group, a urethane groupand a urea group, or a combination of two or more of them; and m″ is 1,2 or 3, n″ is 0, 1 or 2, and the sum of m″ and n″ is 3.

(16) The positive type photoresist composition described in the above(15), wherein said resin is a copolymer containing repeating units of amonomer represented by general formula [I-4] and a monomer having analicyclic hydrocarbon moiety in its molecule.

(17) The positive type photoresist composition described in the above(15) or (16), wherein the active light ray or the radiation for exposurehas a wavelength of 170 nm to 220 nm.

(18) The-positive type photoresist composition described in the above(15) or (16), wherein said resin further contains repeating structuralunits each having a group which is decomposed by action of an acid toincrease solubility in an alkali developing solution.

(19) The positive type photoresist composition described in any one ofthe above (15) to (17), wherein said composition is composed so as togive a transmission optical density of 1.0 or less per micron of coatedlayer in thickness to an active light ray having a wavelength of 193 nm.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail below.

The alkyl groups represented by R₁ to R₃ in general formula [I] arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyl,butyl, isobutyl and sec-butyl, more preferably, methyl, ethyl, propyl,isopropyl and butyl, and most preferably methyl and ethyl. Thecycloalkyl groups include cyclopentyl, cyclohexyl and cyclooctyl, andpreferably, cyclopentyl and cyclohexyl.

The alkyl groups represented by R₄ are preferably alkyl groups eachhaving 1 to 8 carbon atoms, more preferably alkyl groups having 1 to 6carbon atoms, and most preferably methyl, ethyl, propyl and butylgroups. The cycloalkyl groups include cyclopentyl, cyclohexyl andcyclooctyl groups, and preferably, cyclopentyl and cyclohexyl groups.

R₂ and R₃, or R₄ and R₂ or R₃ may combine together by an alkylene chainto form a ring. Such rings include cyclopentyl, cyclohexyl andcyclooctyl groups.

A is preferably a sulfur atom, although the details thereof are unknown.

The group represented by general formula [I] contains a protectivegroup, is excellent in eliminating ability of a protective group moietyaccording to an acid generated with a photo acid generator, and is notexcessively decomposed during storage. Accordingly, the high sensitivityis compatible with the excellent aging storage stability in the resistcomposition using the resin containing that group.

Raw material resins for the resins containing the groups represented bythe above-mentioned general formula [I] may be any, as long as theyprovide the effects of the present invention.

In the present invention, as the resins containing the groupsrepresented by general formula [I], the resins containing the repeatingstructural units represented by the above-mentioned general formula [II]are preferred. These resins can be obtained, for example, by radicalpolymerization of monomers corresponding to the repeating structuralunits represented by the above-mentioned general formula [II].

X in the above-mentioned general formula [II] is a single bond, or onegroup selected from an alkylene group, a substituted alkylene group, anether group, a thioether group, a carbonyl group, an ester group, anamido group, a sulfonamido group, a urethane group and a urea group, ora combination of two or more of them. The alkylene groups and thesubstituted alkylene groups include-groups shown below:

wherein R and R′, which may be the same or different, each represents ahydrogen atom, an alkyl group, a substituted alkyl group, a halogenatom, a hydroxyl group or an alkoxyl group. The alkyl groups arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyland butyl, and more preferably, methyl, ethyl, propyl and isopropyl.Substituent groups of the substituted alkyl groups include halogen atomsand hydroxyl and alkoxyl groups. The alkoxyl groups include groupshaving 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy.n represents an integer of 1 to 10.

Of the above, X is particularly preferably a single bond, or one groupselected from an alkylene group, a substituted alkylene group, an ethergroup, a thioether group, a carbonyl group and an ester group, or acombination of two or more of them. The alkylene groups are preferablyalkylene groups each having 1 to 4 carbon atoms herein, and specificexamples thereof include methylene, ethylene, propylene, butylene,methyl-substituted methylene, dimethyl-substituted methylene,methyl-substituted ethylene, dimethyl-substituted ethylene,methyl-substituted propylene and dimethyl-substituted propylene.

Preferred examples of the repeating structural units represented bygeneral formula [II] include repeating structural units represented bythe following general formulas [II-A] to [II-K]:

In the above-mentioned general formulas, R₁ to R₅, R, R′, A and n havethe same meanings as given above, and m represents an integer of 1 to 3.

Specific examples of monomers corresponding to the repeating structuralunits represented by general formula [II] are enumerated below, but donot limit the scope of the present invention:

Such monomers corresponding to the repeating structural unitsrepresented by general formula [II] can be generally obtained byreacting carboxylic anhydrides having radical-polymerizablecarbon-carbon bonds or carboxylic acid chlorides with alkoxy- ormercapto-substituted alcohol compounds under basic conditions.

It is preferred that the resins used in the positive type photoresistcompositions of the present invention contain the repeating units havingalicyclic hydrocarbon moieties in their molecules, as well as the groupsrepresented by the above-mentioned general formula [I]. This can enhancethe resistance to dry etching of the positive photoresists. Therepeating structural units having alicyclic hydrocarbon moieties intheir molecules include, for example, repeating structural unitsrepresented by the above-mentioned general formulas [III] and [IV].

R₆ in general formula [III] is a monovalent alicyclic hydrocarbon group.Specifically, such groups include an adamantyl group, a2-methyl-2-adamantyl group, a norbornyl group, a bornyl group, anisobornyl group, a tricyclo-decanyl group, a dicyclopentenyl group, anorbornaneepoxy group, a menthyl group, an isomenthyl group and aneomenthyl group.

In general formula [IV], R₇ is a connecting group having a divalentalicyclic hydrocarbon moiety. The alicyclic hydrocarbon moietiescontained in the connecting groups represented by R₇ include, forexample, the following structures:

The connecting group in R₇ connecting the above-mentioned alicyclichydrocarbon moiety and the ester group, or above-mentioned alicyclichydrocarbon moiety and the group represented by G, which may be a singlebond, includes one group selected from an alkylene group, an ethergroup, a thioether group, a carbonyl group, an ester group, an amidogroup and a sulfonamide group, or a combination of two or more of them.

R₈ in the —COOR₈ or —OR₈ group represents a substituent groupdecomposable by the action of an acid. Examples of such groups includetertiary alkyl groups such as t-butyl and t-amyl, 1-alkoxyethyl groupssuch as tetrahydropyranyl, tetrahydrofuranyl, —CH(CH₃)OCH₂CH₃ and—CH(CH₃)OCH₂CH(CH₃)₂, and alkoxymethyl groups such as —CH₂OCH₃ and—CH₂OCH₂CH₃.

In the above-mentioned resins, the content of the repeating structuralunits containing the groups represented by general formula [I] ispreferably 5 mol % to 80 mol %, and more preferably 10 mol % to 70 mol%, based on the total repeating units. Less than 5 mol % is unfavorablebecause the effect of the present invention is difficult to be achieved.Exceeding 80 mol % unfavorably results in liability to deteriorate theresistance to dry etching.

The content of the repeating structural units having alicyclichydrocarbon moieties in their molecules contained in the resins is 20mol % to 95 mol %, and preferably 30 mol % to 90 mol %, based on thetotal repeating units.

The above-mentioned resins used in the present invention may furthercontain repeating structural units corresponding to the followingconventional monomers containing acid decomposable groups other than thegroups represented by general formula [I].

Examples of the conventional monomers include t-butyl acrylate, t-butylmethacrylate, t-amyl acrylate, t-amyl methacrylate, tetrahydrofuranylacrylate, tetrahydrofuranyl methacrylate, tetrahydropyranyl acrylate,tetrahydropyranyl methacrylate, alkoxymethyl acrylate, alkoxymethylmethacrylate and 1-alkoxyethyl methacrylate.

In the above-mentioned resins, the content of the repeating structuralunits corresponding to such conventional monomers having aciddecomposable groups is preferably 99 mol % or less, more preferably 90mol % or less, and most preferably 80 mol % or less, based on the totalmolar number of the repeating structural units having the groupsrepresented by the above-mentioned general formula [I]. Exceeding 99 mol% is unfavorable because the effect of the present invention is notsufficiently manifested.

Such resins can be further copolymerized with the following monomers asrepeating units within the range in which the effect of the presentinvention can be effectively obtained. However, the present invention isnot limited thereto.

This enables fine adjustment of properties required for theabove-mentioned resins, particularly (1) solubility in coating solvents,(2) film forming properties (glass transition temperature), (3) alkalideveloping properties, (4) film thickness loss (hydrophilic andhydrophobic properties, selection of alkali-soluble groups), (5)adhesion of unexposed areas to substrates and (6) resistance to dryetching.

Such monomers for copolymerization include, for example, compounds eachhaving one addition-polymerizable unsaturated bond, selected fromacrylic esters, methacrylic esters, acrylamide compounds, methacrylamidecompounds, allyl compounds, vinyl ethers and vinyl esters.

Specifically, examples of the acrylic esters include alkyl acrylates(wherein alkyl groups each preferably has 1 to 10 carbon atoms) (such asmethyl acrylate, ethyl acrylate, propyl acrylate, t-butyl acrylate, amylacrylate, cyclohexyl acrylate, ethylhexyl acrylate, octyl acrylate,t-octyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate,2,2-dimetylhydroxypropyl acrylate, 5-hydroxypentyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzylacrylate, methoxybenzyl acrylate, furfuryl acrylate andtetrahydrofurfuryl acrylate).

Examples of the methacrylic esters include alkyl methacrylates (whereinalkyl groups each preferably has 1 to 10 carbon atoms) (such as methylmethacrylate, ethyl methacrylate, propyl methacrylate, isopropylmethacrylate, t-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzylmethacrylate, octyl methacrylate, 2-hydroxyethyl methacrylate,4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate,2,2-dimethyl-3-hydroxypropyl methacrylate, trimethylolpropanemonomethacrylate, pentaerythritol monomethacrylate, furfurylmethacrylate and tetrahydrofurfuryl methacrylate).

Examples of the acrylamide compounds include acrylamide,N-alkylacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, propyl, butyl, t-butyl,heptyl, octyl, cyclohexyl and hydroxyethyl), N,N-dialkylacrylamides(wherein alkyl groups each preferably has 1 to 10 carbon atoms, forexample, methyl, ethyl, butyl, isobutyl, ethylhexyl and cyclohexyl),N-hydroxyethyl-N-methylacrylamide andN-2-acetamidoethyl-N-acetylacrylamide.

Examples of the methacrylamide compounds include methacrylamide,N-alkylmethacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, t-butyl, ethylhexyl,hydroxyethyl and cyclohexyl), N,N-dialkylmethacrylamides (wherein alkylgroups are, for example, ethyl, propyl and butyl) andN-hydroxyethyl-N-methylmethacrylamide.

Examples of the allyl compounds include allyl esters (such as allylacetate, allyl caproate, allyl caprylate, allyl laurate, allylpalmitate, allyl stearate, allyl benzoate, allyl acetoacetate and allyllactate) and allyloxyethanol.

Examples of the vinyl ethers include alkyl vinyl ethers (such as hexylvinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinylether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethylvinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinylether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether,dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether,butylaminoethyl vinyl ether, benzyl vinyl ether and tetrahydrofurfurylvinyl ether).

Examples of the vinyl esters include vinyl butyrate, vinyl isobutyrate,vinyl trimethylacetate, vinyl diethylacetate, vinyl valerate, vinylcaproate, vinyl chloroacetate, vinyl dichloroacetate, vinylmethoxyacetate, vinyl butoxyacetate, vinyl acetoacetate, vinyl lactate,vinyl β-phenylbutyrate and vinyl cyclohexylcarboxylate.

The monomers also include dialkyl itaconates (such as dimethylitaconate, diethyl itaconate and dibutyl itaconate), dialkyl esters ofmaleic acid or fumaric acid (such as dimethyl maleate and dibutylfumarate) and monoalkyl esters thereof, acrylic acid, methacrylic acid,crotonic acid, itaconic acid, maleic anhydride, maleimide,acrylonitrile, methacrylonitrile and maleylonitrile.

In addition, any monomers may be used, as long as they areaddition-polymerizable unsaturated compounds copolymerizable with therepeating structural units represented by general formula [I].

The content of the repeating structural units corresponding to theadditional monomers as described above is preferably 99 mol % or less,more preferably 90 mol % or less, and most preferably 80 mol % or less,based on the total molar number of the repeating structural unitsrepresented by general formula [I] and the repeating structural unitshaving alicyclic hydrocarbon moieties. Exceeding 99 mol % is unfavorablebecause the effect of the present invention is not sufficientlymanifested.

The above-mentioned resins can be represented, for example, by thefollowing general formula [V], but the scope of the present invention isnot limited thereto.

wherein R₁ to R₇, A, X and G have the same meanings as given above; R₁₀represents a tertiary alkyl group, a tetrahydropyranyl group, atetrahydrofuranyl group, an alkoxyethyl group, an alkoxymethyl group, a3-oxocyclohexyl group, or a 2-oxocyclohexyl group; R₁₁ represents amethyl group, an ethyl group, a propyl group, an iso-propyl group or an-butyl group; a is 5 to 80; b is 0 to 70; c is 0 to 95; d, e and f areeach 0 to 50; a+d≧30; b+c≧50; a+b+c+d+e+f=100; a>d; and a+b+c>e+f.

The weight-average molecular weight of the above-mentioned resins usedin the present invention is preferably 2,000 to 200,000. If theweight-average molecular weight is less than 2,000, deterioration inheat resistance and resistance to dry etching is unfavorably observed.Exceeding 200,000 brings about unfavorable results such as deteriorationin developing properties, and deterioration in film forming propertiescaused by an extreme increase in viscosity.

The resins used in the present invention can be synthesized by usualmethods including radical polymerization using azo compounds asinitiators.

The positive type photoresist compositions of the present inventionmainly contain the above-mentioned resins and photo acid generators. Theamount of the resin added to the whole composition is 40% to 99% byweight, and preferably 50% to 97% by weight, based on the total solidcontent of the resist.

The alkyl groups represented by R₂₁ to R₂₄ in general formula [I-2] arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyl,butyl, isobutyl and sec-butyl, more preferably, methyl, ethyl, propyl,isopropyl and butyl, and most preferably methyl and ethyl.

m represents 1 or 2, and preferably 1.

Raw material resins for the resins containing the groups represented bythe above-mentioned general formula [I-2] may be any, as long as theyprovide the effects of the present invention.

In the present invention, as the resins containing the groupsrepresented by general formula [I-2], the resins containing therepeating structural units represented by the above-mentioned generalformula [II-2] are preferred. These resins can be obtained, for example,by radical polymerization of monomers corresponding to the repeatingstructural units represented by the above-mentioned general formula[II-2].

A₂₁ in the above-mentioned general formula [II-2] is a single bond, orone group selected from an alkylene group, a substituted alkylene group,an ether group, a thioether group, a carbonyl group, an ester group, anamido group, a sulfonamido group, a urethane group and a urea group, ora combination of two or more of them. The alkylene groups and thesubstituted alkylene groups represented by A₂₁ include groups shownbelow:

wherein R and R′, which may be the same or different, each represents ahydrogen atom, an alkyl group, a substituted alkyl group, a halogenatom, a hydroxyl group or an alkoxyl group. The alkyl groups arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyland butyl, and more preferably, methyl, ethyl, propyl and isopropyl.Substituent groups of the substituted alkyl groups include halogen atomsand hydroxyl and alkoxyl groups. The alkoxyl groups include groupshaving 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy.n represents an integer of 1 to 10.

Of the above, A₂₁ is particularly preferably a single bond, or one groupselected from an alkylene group, a substituted alkylene group, an ethergroup, an ester group, an amido group, a urethane group and a ureagroup, or a combination of two or more of them. The alkylene groups andthe substituted alkylene groups are preferably alkylene groups eachhaving 1 to 4 carbon atoms herein, and specific examples thereof includemethylene, ethylene, propylene, butylene, methyl-substituted methylene,dimethyl-substituted methylene, methyl-substituted ethylene,dimethyl-substituted ethylene, methyl-substituted propylene anddimethyl-substituted propylene.

Preferred examples of the monomers represented by general formula [II-2]include monomers represented by the following general formulas [II-A′]to [II-I′]:

In the above-mentioned general formulas, R₂₁ to R₂₅, R, R′, n and m havethe same meanings as given above, and p represents an integer of 1 to 3.

Specific examples of the monomers represented by general formula [II]are enumerated below, but do not limit the scope of the presentinvention:

Such monomers represented by general formula [II-2] can be synthesizedby esterifying carboxylic acids having radical-polymerizablecarbon-carbon bonds in their molecules with 2-hydroxylactones by themethod described in Angew. Chem. int. Ed. Engl., 17, 522 (1978), or byreacting the corresponding carboxylic acid chlorides with2-hydroxylactones under basic conditions.

It is preferred that the resins used in the positive type photoresistcompositions of the present invention contain the repeating units havingalicyclic hydrocarbon moieties in their molecules, as well as the groupsrepresented by the above-mentioned general formula [I]. This can enhancethe resistance to dry etching of the positive photoresists. Therepeating structural units having alicyclic hydrocarbon moieties intheir molecules include, for example, repeating structural unitsrepresented by the above-mentioned general formulas [III] and [IV].

In the above-mentioned resins, the content of the repeating structuralunits containing the groups represented by general formula [I-2] ispreferably 3 mol % to 60 mol %, and more preferably 5 mol % to 50 mol %,based on the total repeating units. Less than 3 mol % is unfavorablebecause the effect of the present invention is difficult to be achieved.Exceeding 60 mol % unfavorably results in liability to deteriorate theresistance to dry etching.

The content of the repeating structural units having alicyclichydrocarbon moieties in their molecules contained in the resins is 40mol % to 97 mol %, and preferably 50 mol % to 95 mol %, based on thetotal repeating units.

It is preferred that the above-mentioned resins used in the presentinvention further contain groups which are decomposed by the action ofacids to increase solubility in alkali developing solutions (alsoreferred to as acid decomposable groups), in addition to the repeatingstructural units having alicyclic hydrocarbon moieties. This makes theeffect of improving sensitivity more significant.

Preferred examples of such acid decomposable groups include —COOR₈,—OR₈, a 3-oxocyclohexyl group and a 2-oxocyclohexyl group as describedabove.

Specifically, examples thereof include repeating structural unitscorresponding to conventional monomers such as t-butyl acrylate, t-butylmethacrylate, t-amyl acrylate, t-amyl methacrylate, tetrahydrofuranylacrylate, tetrahydrofuranyl methacrylate, tetrahydropyranyl acrylate,tetrahydropyranyl methacrylate, alkoxymethyl acrylate, alkoxymethylmethacrylate, 1-alkoxyethyl methacrylate, 3-oxocyclohexyl acrylate,3-oxocyclohexyl methacrylate, 2-oxocyclohexyl acrylate and2-oxocyclohexyl methacrylate.

As to the content of the repeating structural units corresponding to themonomers having such conventional acid decomposable groups in theabove-mentioned resins, the conventional acid decomposablegroups/repeating structural units having groups represented by theabove-mentioned general formula [I] is preferably 6/1 or less, and morepreferably 3/1 or less. If this value exceeds 6/1, the effect of thepresent invention is not sufficiently manifested to bring about anunfavorable result.

Such resins can be further copolymerized with the following monomers asrepeating units within the range in which the effect of the presentinvention can be effectively obtained. However, the present invention isnot limited Cello thereto.

This enables fine adjustment of properties required for theabove-mentioned resins, particularly (1) solubility in coating solvents,(2) film forming properties (glass transition temperature), (3) alkalideveloping properties, (4) film thickness loss (hydrophilic andhydrophobic properties, selection of alkali-soluble groups), (5)adhesion of unexposed areas to substrates and (6) resistance to dryetching, as described above.

Such monomers for copolymerization include, for example, compounds eachhaving one addition-polymerizable unsaturated bond, selected fromacrylic esters, methacrylic esters, acrylamide compounds, methacrylamidecompounds, allyl compounds, vinyl ethers and vinyl esters.

Specifically, examples of the acrylic esters include alkyl acrylates(wherein alkyl groups each preferably has 1 to 10 carbon atoms) (such asmethyl acrylate, ethyl acrylate, propyl acrylate, amyl acrylate,cyclohexyl acrylate, ethylhexyl acrylate, octyl acrylate, t-octylacrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate,2,2-dimetylhydroxypropyl acrylate, 5-hydroxypentyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzylacrylate, methoxybenzyl acrylate, furfuryl acrylate andtetrahydrofurfuryl acrylate).

Examples of the methacrylic esters include alkyl methacrylates (whereinalkyl groups each preferably has 1 to 10 carbon atoms) (such as methylmethacrylate, ethyl methacrylate, propyl methacrylate, isopropylmethacrylate, amyl methacrylate, hexyl methacrylate, cyclohexylmethacrylate, benzyl methacrylate, chlorobenzyl methacrylate, octylmethacrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl methacrylate,5-hydroxypentyl methacrylate, 2,2-dimethyl-3-hydroxypropyl methacrylate,trimetylolpropane monomethacrylate, pentaerythritol monomethacrylate,furfuryl methacrylate and tetrahydrofurfuryl methacrylate).

Examples of the acrylamide compounds include acrylamide,N-alkylacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, propyl, butyl, t-butyl,heptyl, octyl, cyclohexyl and hydroxyethyl), N,N-dialkylacrylamides(wherein alkyl groups each preferably has 1 to 10 carbon atoms, forexample, methyl, ethyl, butyl, isobutyl, ethylhexyl and cyclohexyl),N-hydroxyethyl-N-methylacrylamide andN-2-acetamidoethyl-N-acetylacrylamide.

Examples of the methacrylamide compounds include methacrylamide,N-alkylmethacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, t-butyl, ethylhexyl,hydroxyethyl and cyclohexyl), N,N-dialkylmethacrylamides (wherein alkylgroups are, for example, ethyl, propyl and butyl) andN-hydroxyethyl-N-methylmethacrylamide.

Examples of the allyl compounds include allyl esters (such as allylacetate, allyl caproate, allyl caprylate, allyl laurate, allylpalmitate, allyl stearate, allyl benzoate, allyl acetoacetate and allyllactate) and allyloxyethanol.

Examples of the vinyl ethers include alkyl vinyl ethers (such as hexylvinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinylether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethylvinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinylether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether,dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether,butylaminoethyl vinyl ether, benzyl vinyl ether and tetrahydrofurfurylvinyl ether).

Examples of the vinyl esters include vinyl butyrate, vinyl isobutyrate,vinyl trimethylacetate, vinyl diethylacetate, vinyl valerate, vinylcaproate, vinyl chloroacetate, vinyl dichloroacetate, vinylmethoxyacetate, vinyl butoxyacetate,. vinyl acetoacetate, vinyl lactate,vinyl β-phenylbutyrate and vinyl cyclohexylcarboxylate.

The monomers also include dialkyl itaconates (such as dimethylitaconate, diethyl itaconate and dibutyl itaconate), dialkyl esters ofmaleic acid or fumaric acid (such as dimethyl maleate and dibutylfumarate) and monoalkyl esters thereof, acrylic acid, methacrylic acid,crotonic acid, itaconic acid, maleic anhydride, maleimide,acrylonitrile, methacrylonitrile and maleylonitrile.

In addition, any monomers may be used, as long as they areaddition-polymerizable unsaturated compounds copolymerizable with therepeating structural units represented by general formula [I-2].

The content of the repeating structural units corresponding to theadditional monomers as described above is preferably 99 mol % or less,more preferably 90 mol % or less, and most preferably 80 mol % or less,based on the total molar number of the repeating structural unitsrepresented by general formula [I-2] and the repeating structural unitshaving alicyclic hydrocarbon moieties. Exceeding 99 mol % is unfavorablebecause the effect of the present invention is not sufficientlymanifested.

The above-mentioned resins can be represented, for example, by thefollowing general formula [V′], but the scope of the present inventionis not limited thereto.

wherein R₂₁ to R₂₅, R₆, R₇, A₂₁ and G have the same meanings as givenabove; R₂₁₀ represents a tertiary alkyl group, a tetrahydropyranylgroup, a tetrahydrofuranyl group, an alkoxyethyl group, an alkoxymethylgroup, a 3-oxocyclohexyl group, or a 2-oxocyclohexyl group; R₂₁₁represents a methyl group, an ethyl group, a propyl group, an iso-propylgroup or a n-butyl group; a′ is 5 to 80; b′ is 0 to 70; c′ is 0 to 95;d′, e′ and f′ are each 0 to 50; a′+d′≧5; b′+c′≧40; anda′+b′+c′+d′+e′+f′=100.

The weight-average molecular weight of the above-mentioned resins usedin the present invention is preferably 2,000 to 200,000. If theweight-average molecular weight is less than 2,000, deterioration inheat resistance and resistance to dry etching is unfavorably observed.Exceeding 200,000 brings about unfavorable results such as deteriorationin developing properties, and deterioration in film forming propertiescaused by an extreme increase in viscosity.

The resins used in the present invention can be synthesized by usualmethods including radical polymerization using azo compounds asinitiators.

The positive type photoresist compositions of the present inventionmainly contain the above-mentioned resins and photo acid generators. Theamount of the resin added to the whole composition is 40% to 99% byweight, and preferably 50% to 97% by weight, based on the total solidcontent of the resist.

Then, the resins which are decomposed by the action of acids to increasesolubility in alkali developing solutions, namely the polymerscontaining the repeating structural units represented by general formula[I-3], are described. In general formula [I-3], R₃₁ represents ahydrogen atom or a methyl group; R₃₂ to R₃₄, which may be the same ordifferent, each represents a hydrogen atom or an alkyl group; R₃₅ andR₃₆, which may be the same or different, each represents a hydrogenatom, an alkyl group or X₃₁R₃₇ wherein R₃₇ is a hydrogen atom or analkyl group, and X₃₁ is an oxygen atom or a sulfur atom. The alkylgroups represented by R₃₂ to R₃₇ are preferably lower alkyl groups suchas methyl, ethyl, propyl, isopropyl, butyl, isobutyl and sec-butyl, morepreferably methyl, ethyl, propyl, isopropyl and butyl, and mostpreferably methyl and ethyl.

m′ is 1, 2 or 3, n′ is 0, 1 or 2, and the sum of m′ and n′ is 3.

A₃₁ represents one group selected from the group consisting of a singlebond, an alkylene group, a substituted alkylene group, an ether group,an ester group, an amido group, a sulfonamido group, a urethane groupand a urea group, or a combination of two or more of them.

The alkylene groups and the substituted alkylene groups represented byA₃₁ include groups shown below:

wherein R and R′, which may be the same or different, each represents ahydrogen atom, an alkyl group, a substituted alkyl group, a halogenatom, a hydroxyl group or an alkoxyl group. The alkyl groups arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyland butyl, and more preferably, methyl, ethyl, propyl and isopropyl.Substituent groups of the substituted alkyl groups include halogen atomsand hydroxyl and alkoxyl groups. The alkoxyl groups include groupshaving 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy.a represents an integer of 1 to 10.

Of the above, A₃₁ is particularly preferably a single bond, or one groupselected from an alkylene group, a substituted alkylene group, an ethergroup, an amido group, a urea group, a urethane group and an estergroup, or a combination of two or more of them. The alkylene groups andthe substituted alkylene groups are preferably alkylene groups eachhaving 1 to 4 carbon atoms herein, and specific examples thereof includemethylene, ethylene, propylene, butylene, methyl-substituted methylene,dimethyl-substituted methylene, methyl-substituted ethylene,dimethyl-substituted ethylene, methyl-substituted propylene anddimethyl-substituted propylene.

Preferred examples of the monomers represented by general formula [I]include monomers represented by the following general formulas [I-A] to[I-K]:

In the above-mentioned general formulas, R₃₁ to R₃₇, R, R′, n′, m′ and ahave the same meanings as given above, and b represents-an integer of 1to 3.

Specific examples of the monomers represented by general formula [I-3]are enumerated below, but do not limit the scope of the presentinvention:

The monomers represented by general formula [I-3] can be synthesized byesterifying carboxylic acids having radical-polymerizable carbon-carbonbonds in their molecules with 2-hydroxylactones by the method describedin Angew. Chem. int. Ed. Engl., 17, 522 (1978), or by reacting thecorresponding carboxylic acid chlorides with 2-hydroxylactones underbasic conditions.

Further, the resins which are decomposed by the action of acids toincrease solubility in alkali developing solutions, namely the polymerscontaining the repeating structural units represented by general formula[I-4], are described. In general formula [I-4], R₄₁ represents ahydrogen atom or a methyl group; R₄₂ to R₄₄, which may be the same ordifferent, each represents a hydrogen atom or an alkyl group; R₄₅ andR₄₆, which may be the same or different, each represents a hydrogenatom, an alkyl group or a halogen atom; and X₄₁ is a halogen atom. Thealkyl groups represented by R₄₂ to R₄₆ are preferably lower alkyl groupssuch as methyl, ethyl, propyl, isopropyl, butyl, isobutyl and sec-butyl,more preferably methyl, ethyl, propyl, isopropyl and butyl, and mostpreferably methyl and ethyl. X₄₁ is a chlorine, bromine or iodine ion.m″ is 1, 2 or 3, n″ is 0, 1 or 2, and the sum of m″ and n″ is 3.

A₄₁ represents one group selected from the group consisting of a singlebond, an alkylene group, a substituted alkylene group, an ether group,an ester group, a thioether group, a carbonyl group, an amido group, asulfonamido group, a urethane group and a urea group, or a combinationof two or more of them. The alkylene groups and the substituted alkylenegroups represented by A₄₁ include groups shown below:

wherein R and R′, which may be the same or different, each represents ahydrogen atom, an alkyl group, a substituted alkyl group, a halogenatom, a hydroxyl group or an alkoxyl group. The alkyl groups arepreferably lower alkyl groups such as methyl, ethyl, propyl, isopropyland butyl, and more preferably, methyl, ethyl, propyl and isopropyl.Substituent groups of the substituted alkyl groups include halogen atomsand hydroxyl and alkoxyl groups. The alkoxyl groups include groupshaving 1 to 4 carbon atoms such as methoxy, ethoxy, propoxy and butoxy.n represents an integer of 1 to 10.

Of the above, A₄₁ is particularly preferably a single bond, or one groupselected from an alkylene group, a substituted alkylene group, an amidogroup, a urethane group, a urea group, an ether group and an estergroup, or a combination of two or more of them. The alkylene groups andthe substituted alkylene groups are preferably alkylene groups eachhaving 1 to 4 carbon atoms herein, and specific examples thereof includemethylene, ethylene, propylene, butylene, methyl-substituted methylene,dimethyl-substituted methylene, methyl-substituted ethylene,dimethyl-substituted ethylene, methyl-substituted propylene anddimethyl-substituted propylene.

Preferred examples of the monomers represented by general formula [I-4]include monomers represented by the following general formulas [I-A′] to[I-K′]:

In the above-mentioned general formulas, R₄₂ to R₄₇, R, R′, n and m havethe same meanings as given above, and a and b each represents an integerof 1 or 2.

Specific examples of the monomers represented by general formula [I-4]are enumerated below, but do not limit the scope of the presentinvention:

Such monomers represented by general formula [I-4] can be synthesized byesterifying carboxylic acids having radical-polymerizable carbon-carbonbonds in their molecules with 2-hydroxylactones by the method describedin Angew. Chem. int. Ed. Engl., 17, 522 (1978), or by reacting thecorresponding carboxylic acid chlorides with 2-hydroxylactones underbasic conditions.

It is preferred that the resins used in the positive type photoresistcompositions of the present invention contain the repeating units havingalicyclic hydrocarbon moieties in their molecules, as well as the groupsrepresented by the above-mentioned general formulas [I-3] and [I-4].This can enhance the resistance to dry etching of the positivephotoresists. The repeating structural units having alicyclichydrocarbon moieties in their molecules include, for example, repeatingstructural units represented by the above-mentioned general formulas[III] and [IV].

In the above-mentioned resins, the content of the repeating structuralunits containing the groups represented by general formula [I-3] or[I-4] is preferably 5 mol % to 80 mol %, and more preferably 10 mol % to70 mol %, based on the total repeating units. Less than 5 mol % isunfavorable because the effect of the present invention is difficult tobe achieved. Exceeding 80 mol % unfavorably results in liability todeteriorate the resistance to dry etching.

The content of the repeating structural units having alicyclichydrocarbon moieties in their molecules contained in the resins is 20mol % to 95 mol %, and preferably 30 mol % to 90 mol %, based on thetotal repeating units.

It is preferred that the above-mentioned resins used in the presentinvention further contain groups which are decomposed by the action ofacids to increase solubility in alkali developing solutions (alsoreferred to as acid decomposable groups), in addition to the groupsrepresented by general formula [I-3] or [I-4] and the repeatingstructural units having alicyclic hydrocarbon moieties. This makes theeffect of improving sensitivity more significant.

Preferred examples of such acid decomposable groups include —COOR₁₁,—OR₁₁, a 3-oxocyclohexyl group and a 2-oxocyclohexyl group as describedabove.

Specifically, examples thereof include repeating structural unitscorresponding to conventional monomers such as t-butyl acrylate, t-butylmethacrylate, t-amyl acrylate, t-amyl methacrylate, tetrahydrofuranylacrylate, tetrahydrofuranyl methacrylate, tetrahydropyranyl acrylate,tetrahydropyranyl methacrylate, alkoxymethyl acrylate, alkoxymethylmethacrylate, 1-alkoxyethyl methacrylate, 3-oxocyclohexyl acrylate,3-oxocyclohexyl methacrylate, 2-oxocyclohexyl acrylate and2-oxocyclohexyl methacrylate.

In the above-mentioned resins, the content of the repeating structuralunits corresponding to such conventional mol % or less, more preferably90 mol % or less, and most preferably 80 mol % or less, based on thetotal molar number of the repeating structural units having the groupsrepresented by the above-mentioned general formula [I-3] or [I-4].Exceeding 99 mol % is unfavorable because the effect of the presentinvention is not sufficiently manifested.

Such resins can be further copolymerized with the following monomers asrepeating units within the range in which the effect of the presentinvention can be effectively obtained. However, the present invention isnot limited thereto.

This enables fine adjustment of properties required for theabove-mentioned resins, particularly (1) solubility in coating solvents,(2) film forming properties (glass transition temperature), (3) alkalideveloping properties, (4) film thickness loss (hydrophilic andhydrophobic properties, selection of alkali-soluble groups), (5)adhesion of unexposed areas to substrates and (6) resistance to dryetching.

Such monomers for copolymerization include, for example, compounds eachhaving one addition-polymerizable unsaturated bond, selected fromacrylic esters, methacrylic esters, acrylamide compounds, methacrylamidecompounds, allyl compounds, vinyl ethers and vinyl esters.

Specifically, examples of the acrylic esters include alkyl acrylates(wherein alkyl groups each preferably has 1 to 10 carbon atoms) (such asmethyl acrylate, ethyl acrylate, propyl acrylate, t-butyl acrylate, amylacrylate, cyclohexyl acrylate, ethylhexyl acrylate, octyl acrylate,t-octyl acrylate, chloroethyl acrylate, 2-hydroxyethyl acrylate,2,2-dimetylhydroxypropyl acrylate, 5-hydroxypentyl acrylate,trimethylolpropane monoacrylate, pentaerythritol monoacrylate, benzylacrylate, methoxybenzyl acrylate, furfuryl acrylate andtetrahydrofurfuryl acrylate).

Examples of the methacrylic esters include alkyl methacrylates (whereinalkyl groups each preferably has 1 to 10 carbon atoms) (such as methylmethacrylate, ethyl methacrylate, propyl methacrylate, isopropylmethacrylate, t-butyl methacrylate, amyl methacrylate, hexylmethacrylate, cyclohexyl methacrylate, benzyl methacrylate, chlorobenzylmethacrylate, octyl methacrylate, 2-hydroxyethyl methacrylate,4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate,2,2-dimethyl-3-hydroxypropyl methacrylate, trimetylolpropanemonomethacrylate, pentaerythritol monomethacrylate, furfurylmethacrylate and tetrahydrofurfuryl methacrylate).

Examples of the acrylamide compounds include acrylamide,N-alkylacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, propyl, butyl, t-butyl,heptyl, octyl, cyclohexyl and hydroxyethyl), N,N-dialkylacrylamides(wherein alkyl groups each preferably has 1 to 10 carbon atoms, forexample, methyl, ethyl, butyl, isobutyl, ethylhexyl and cyclohexyl),N-hydroxyethyl-N-methylacrylamide andN-2-acetamidoethyl-N-acetylacrylamide.

Examples of the methacrylamide compounds include methacrylamide,N-alkylmethacrylamides (wherein alkyl groups each preferably has 1 to 10carbon atoms, for example, methyl, ethyl, t-butyl, ethylhexyl,hydroxyethyl and cyclohexyl), N,N-dialkylmethacrylamides (wherein alkylgroups are, for example, ethyl, propyl and butyl) andN-hydroxyethyl-N-methylmethacrylamide.

Examples of the allyl compounds include allyl esters (such as allylacetate, allyl caproate, allyl caprylate, allyl laurate, allylpalmitate, allyl stearate, allyl benzoate, allyl acetoacetate and allyllactate) and allyloxyethanol.

Examples of the vinyl ethers include alkyl vinyl ethers (such as hexylvinyl ether, octyl vinyl ether, decyl vinyl ether, ethylhexyl vinylether, methoxyethyl vinyl ether, ethoxyethyl vinyl ether, chloroethylvinyl ether, 1-methyl-2,2-dimethylpropyl vinyl ether, 2-ethylbutyl vinylether, hydroxyethyl vinyl ether, diethylene glycol vinyl ether,dimethylaminoethyl vinyl ether, diethylaminoethyl vinyl ether,butylaminoethyl vinyl ether, benzyl vinyl ether and tetrahydrofurfurylvinyl ether).

Examples of the vinyl esters include vinyl butyrate, vinyl isobutyrate,vinyl trimethylacetate, vinyl diethylacetate, vinyl valerate, vinylcaproate, vinyl chloroacetate, vinyl dichloroacetate, vinylmethoxyacetate, vinyl butoxyacetate, vinyl acetoacetate, vinyl lactate,vinyl β-phenylbutyrate and vinyl cyclohexylcarboxylate.

The monomers also include dialkyl itaconates (such as dimethylitaconate, diethyl itaconate and dibutyl itaconate), dialkyl esters ofmaleic acid or fumaric acid (such as dimethyl maleate and dibutylfumarate) and monoalkyl esters thereof, acrylic acid, methacrylic acid,crotonic acid, itaconic acid, maleic anhydride, maleimide,acrylonitrile, methacrylonitrile and maleylonitrile.

In addition, any monomers may be used, as long as they areaddition-polymerizable unsaturated compounds copolymerizable with therepeating structural units represented by general formula [I-3] or[I-4].

The content of the repeating structural units corresponding to theadditional monomers as described above is preferably 99 mol % or less,more preferably 90 mol % or less, and most preferably 80 mol % or less,based on the total molar number of the repeating structural unitsrepresented by general formula [I-3] or [I-4] and the repeatingstructural units having alicyclic hydrocarbon moieties. Exceeding 99 mol% is unfavorable because the effect of the present invention is notsufficiently manifested.

The weight-average molecular weight of the above-mentioned resins usedin the present invention is preferably 2,000 to 200,000. If theweight-average molecular weight is less than 2,000, deterioration inheat resistance and resistance to dry etching is unfavorably observed.Exceeding 200,000 brings about unfavorable results such as deteriorationin developing properties and deterioration in film forming propertiescaused by an extreme increase in viscosity.

As described above, the resins used in the present invention have nogroups strong in photoabsorption in the far ultraviolet region on eithertheir main chains or their side chains, so that irradiated lightsufficiently arrives at around the substrate sides of coated films,which causes high sensitivity and excellent pattern profiles. It goeswithout saying that being low in transmission density is a necessarycondition and does not necessarily results in excellent resistcharacteristics, and that other factors also have influence thereon.However, the resins used in the present invention fulfill this necessarycondition.

The resins used in the present invention can be synthesized by usualmethods including radical polymerization using azo compounds asinitiators.

The positive type photoresist compositions of the present inventionmainly contain the above-mentioned resins and photo acid generators. Theamount of the resin added to the whole composition is 40% to 99% byweight, and preferably 50% to 97% by weight, based on the total solidcontent of the resist.

Then, the photo acid generators contained in the positive typephotoresist compositions of the present invention are described below.

The photo acid generators are required to satisfy two properties, namely(1) transparency to exposure light (in the case that the agents have nophotobleaching property) and (2) sufficient photodecomposability forensuring resist sensitivity. Although guidelines for molecular designfor fulfilling such conflicting requirements are not clear in thepresent circumstances, examples of the photo acid generators includealiphatic alkylsulfonium salts having 2-oxocyclohexyl groups describedin JP-A-7-25846, JP-A-7-28237, JP-A-7-92675 and JP-A-8-27102, andN-hydroxysuccinimide sulfonates. Further, examples thereof includesulfonium salts represented by the following general formula (VI),disulfones represented by the following general formula (VII) andcompounds represented by the following general formula (VIII), which aredescribed in J. Photopolym. Sci. Technol., 7 (3), 423 (1994).

R₁₂—SO₂SO₂—R₁₃  (VII)R₁₄—SO₂—CN₂—SO₂—R₁₅  (VIII)wherein R₁₂ to R₁₅, which may be the same or different, each representsan alkyl group or a cyclic alkyl group.

Further, N-hydroxymaleinimide sulfonates represented by the followinggeneral formula (IX) are also preferred.

wherein R₁₆ and R₁₇, which may be the same or different, each representsa hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or acycloalkyl group having 6 or less carbon atoms, and R₁₆ and R₁₇ maycombine together by an alkylene group to form a ring; and R₁₈ representsan alkyl group, a perfluoroalkyl group, a cycloalkyl group or a camphorsubstituent. Such N-hydroxymaleinimide sulfonates are particularlypreferred in photosensitivity.

In the above-mentioned general formula (IX), the alkyl groups eachhaving 1 to 6 carbon atoms represented by R₁₆ and R₁₇ include methyl,ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl andn-hexyl. Particularly, methyl, ethyl and propyl are preferred, andmethyl and ethyl are more preferred. The cycloalkyl groups each having 6or less carbon atoms include cyclopropyl, cyclopentyl and cyclohexyl.Cyclopentyl and cyclohexyl are preferred. Examples of the formation ofrings with R₁₆ and R₁₇ by alkylene chains include the formation ofcyclohexyl, norbornyl and tricyclodecanyl groups.

The alkyl groups represented by R₁₈ include straight-chain alkyl groupseach having 1 to 20 carbon atoms, including methyl, ethyl and propyl,and branched alkyl groups each having 1 to 20 carbon atoms, includingisopropyl, isobutyl, tert-butyl and neopentyl. Straight-chain orbranched alkyl groups each having 1 to 16 carbon atoms are preferred,and straight-chain or branched alkyl groups each having 4 to 15 carbonatoms are more preferred. The perfluoroalkyl groups includestraight-chain perfluoroalkyl groups each having 1 to 20, includingtrifluoromethyl and pentafluoroethyl, and branched perfluoroalkyl groupseach having 1 to 20, including heptafluoroisopropyl andnonafluoro-tert-butyl. Straight-chain or branched perfluoroalkyl groupseach having 1 to 16 carbon atoms are preferred. The cyclic alkyl groupsinclude monocyclic alkyl groups such as cyclopentyl and cyclohexyl, andpolycyclic alkyl groups such as decalyl, norbornyl and tricyclodecanyl.

The amount of such a photo acid generators added to the composition ispreferably 0.1% to 20% by weight, more preferably 0.3% to 15% by weight,and most preferably 1% to 10% by weight, based on the total solidcontent of the positive type photoresist composition.

In the positive type photoresist compositions of the present invention,photo acid generators as described below may be used in combination, inaddition to the above-mentioned photo acid generators.

The following photo acid generators which can be used in combination areadded to the compositions preferably in an amount of not more than 2% byweight, and more preferably in an amount of not more than 1% by weight,per the solid content of the whole positive type photoresistcomposition.

Examples of such photo acid generators include diazonium salts describedin S. I. Schlesinger, Photogr. Sci. Eng., 18, 387 (1974) and T. S. Balet al., Polymer, 21, 423 (1980), ammonium salts described in U.S. Pat.Nos. 4,069,055, 4,069,056 and Re 27,992, and JP-A-3-140140, phosphoniumsalts described in D. C. Necker et al., Macromolecules, 17, 2468 (1984),C. S. Wen et al., Tec. Ptoc. Conf. Rad. Curing ASIA, p. 478, Tokyo,October (1988), U.S. Pat. Nos. 4,069,055 and 4,069,056, iodonium saltsdescribed in J. V. Crivello et al., Macromolecules, 10 (6), 1307 (1977),Chem. & Eng. News, Nov. 28, 31 (1988), European Patents 104,143, 339,049and 410,201, JP-A-2-150848 and JP-A-2-296514, sulfonium salts describedin J. V. Crivello et al., Polymer, J. 17, 73 (1985), J. V. Crivello etal., J. Org. Chem., 43, 3055 (1978), W. R. Watt et al., J. Polymer Sci.,Polymer Chem. Ed., 22, 1789 (1984), J. V. Crivello et al., PolymerBull., 14, 279 (1985), J. V. Crivello et al., Macromolecules, 14 (5),1141 (1981), J. V. Crivello et al., J. Polymer Sci., Polymer Chem. Ed.,17, 2877 (1979), European Patents 370,693, 161,881, 410,201, 339,049,233,567, 297,443 and 297,442, U.S. Pat. Nos. 3,902,114, 4,933,377,4,760,013, 4,734,444 and 2,833,827, and German Patents 2,904,626,3,604,580 and 3,604,581, selenonium salts described in J. V. Crivello etal., Macromolecules, 10 (6), 1307 (1977) and J. V. Crivello et al., J.Polymer Sci., Polymer Chem. Ed., 17, 1047 (1979), onium salts such asarsonium salts described in C. S. Wen et al., Tec. Ptoc. Conf. Rad.Curing ASIA, p. 478, Tokyo, October (1988), organic halogen compoundsdescribed in U.S. Pat. No. 3,905,815, JP-B-46-4605 (the term “JP-B” asused herein means an “examined Japanese patent publication”),JP-A-48-36281, JP-A-55-32070, JP-A-60-239736, JP-A-61-169835,JP-A-61-169837, JP-A-62-58241, JP-A-62-212401, JP-A-63-70243 andJP-A-63-298339, organic metal/organic halides described in K. Meier etal., J. Rad. Curina, 13 (4), 26 (1986), T. P. Gill et al., Inorg. Chem.,19, 3007 (1980), D. Astruc, Acc. Chem. Res., 19 (12), 377 (1896) andJP-A-2-161445, photo acid generators having o-nitrobenzyl typeprotective groups described in S. Hayase et al., J. Polymer Sci., 25,753 (1987), E. Reichmanis et al., J. Polymer Sci., Polymer Chem. Ed.,23, 1 (1985), Q. Q. Zhu et al., J. Photochem., 36, 85, 39, 317 (1987),B. Amit et al., Tetrahedron Lett., (24), 2205 (1973), D. H. R. Barton etal., J. Chem. Soc., 35, 71 (1965), P. M. Collins et al., J. Chem. Soc.,Perkin I, 1695 (1975), M. Rudinstein et al., Tetrahedron Lett., (17),1445 (1975), J. W. Walker et al., J. Am. Chem. Soc., 110, 7170 (1988),S. C. Busman et al., J. Imaging Technol., 11 (4), 191 (1985), H. M.Houlihan et al., Macromolecules, 21, 2001 (1988), P. M. Collins et al.,J. Chem. Soc., Chem. Commun., 532 (1972), S. Hayase et al.,Macromolecules, 18, 1799 (1985), E. Reichmanis et al., J. Electrochem.Soc., Solid State Sci. Technol., 130 (6), F. M. Houlihan et al.,Macromolecules, 21, 2001 (1988), European Patents 290,750, 046,083,156,535, 271,851 and 388,343, U.S. Pat. Nos. 3,901,710 and 4,181,531,JP-A-60-198538 and JP-A-53-133022, compounds producing sulfonic acids byphotolysis which are represented by iminosulfonates described in M.Tunooka et al., Polymer Preprints Japan, 35 (8), G. Berner et al., J.Rad. Curing, 13 (4), W. J. Mijs et al., Coating Technol., 55 (697), 45(1983), Akzo, H. Adachi et al., Polymer Preprints Japan, 37 (3),European Patents 199,672, 84,515, 44,115, 618,564, and 101,122, U.S.Pat. Nos. 618,564, 4,371,605 and 4,431,774, JP-A-64-18143, JP-A-2-245756and JP-A-3-140109, and disulfone compounds described in JP-A-61-166544.

Further, compounds in which these groups or compounds generating acidswith light are introduced into their main chains or side chains can beused. Examples of such compounds are described in M. E. Woodhouse etal., J. Am. Chem. Soc., 104, 5586 (1982), S. P. Pappas et al., J.Imaging Sci., 30 (5), 218 (1986), S. Kondo et al., Makromol. Chem.,Rapid Commun., 9, 625 (1988), Y. Yamada et al., Makromol. Chem., 152,153, 163 (1972), J. V. Crivello et al., J. Polymer Sci., Polymer Chem.Ed., 17, 3845 (1979), U.S. Pat. No. 3,849,137, German Patent 3,914,407,JP-A-63-26653, JP-A-55-164824, JP-A-62-69263, JP-A-63-146038,JP-A-63-163452, JP-A-62-153853 and JP-A-63-146029.

Further, compounds generating acids with light can also be used whichare described in V. N. R. Pillai Synthesis, (1) 1 (1980), A. Abad etal., Tetrahedron Lett., (47), 4555 (1971), D. H. R. Barton et al., J.Chem. Soc., (C), 329 (1970), U.S. Pat. No. 3,779,778 and European Patent126,712.

Of the above-mentioned compounds which can be used in combination andare decomposed by irradiation of active light rays or radiation togenerate acids, compounds particularly effectively used are describedbelow.

(1) Oxazole derivatives substituted by trihalomethyl groups, which arerepresented by the following general formula (PAG1), or S-triazinederivatives represented by the following general formula (PGA2)

wherein R²⁰¹ represents a substituted or unsubstituted aryl or alkenylgroup; R²⁰² represents a substituted or unsubstituted aryl, alkenyl oralkyl group, or —C(Y)₃; and Y represents a chlorine atom or a bromineatom.

Specific examples thereof include but are not limited to the followingcompounds:

(2) Iodonium salts represented by the following general formula (PAG3)or sulfonium salts represented by the following general formula (PAG4)

wherein Ar¹ and Ar² each independently represents a substituted orunsubstituted aryl group. Preferred examples of the substituent groupsinclude alkyl, haloalkyl, cycloalkyl, aryl, alkoxyl, nitro, carboxyl,alkoxycarbonyl, hydroxyl, mercapto and halogen atoms.

R²⁰³, R²⁰⁴ and R²⁰⁵ each independently represents a substituted orunsubstituted alkyl or aryl group, and preferably an aryl group having 6to 14 carbon atoms, an alkyl group having 1 to 8 carbon atoms or asubstituted derivative thereof. Preferred examples of the substituentgroups for aryl include alkoxyl of 1 to 8 carbon atoms, alkyl of 1 to 8carbon atoms, nitro, carboxyl, hydroxyl and halogen atoms, and preferredexamples thereof for alkyl include alkoxyl of 1 to 8 carbon atoms,carboxyl and alkoxycarbonyl.

Z⁻ represents a counter ion such as a perfluoroalkane-sulfonic acidanion, for example, CF₃SO₃ ⁻, or a pentafluoro-benzenesulfonic acidanion.

Two of R²⁰³, R²⁰⁴ and R²⁰⁵, and Ar¹ and Ar² may combine together by eachsingle bond or substituent group.

Specific examples thereof include but are not limited to the followingcompounds:

The above-mentioned onium salts represented by general formulas (PAG3)and (PAG4) are known, and can be synthesized, for example, by methodsdescribed in J. W. Knapczyk et al., J. Am. Chem. Soc., 91, 145 (1969),A. L. Maycok et al., J. Org. Chem., 35, 2532 (1970), E. Goethas et al.,Bull. Soc. Chem. Belg., 73, 546 (1964), H. M. Leicester, J. Am. Chem.Soc., 51, 3587 (1929), J. V. Crivello et al., J. Polymer Chem. Ed., 18,2677 (1980), U.S. Pat. Nos. 2,807,648 and 4,247,473, and JP-A-53-101331.

(3) Disulfone derivatives represented by the following general formula(PAG5) or iminosulfonate derivatives represented by the-followinggeneral formula (PAG6)

wherein Ar³ and Ar⁴ each independently represents a substituted orunsubstituted aryl group; R²⁰⁶ represents a substituted or unsubstitutedalkyl or aryl group; and A represents a substituted or unsubstitutedalkylene, alkenylene or arylene group.

Specific examples thereof include but are not limited to the followingcompounds:

Appropriate alkali-soluble low molecular weight compounds may be addedto the positive type photoresist compositions for-improving alkalisolubility in the systems or controlling the glass transitiontemperature of the systems to prevent the films from becoming brittleand the heat resistance from being deteriorated. The alkali-soluble lowmolecular weight compounds include compounds having acidic groups intheir molecules such as dialkylsulfonamide compounds,dialkylsulfonylimide (—SO₂—NH—CO—) compounds and dialkyldisulfonylimide(—SO₂—NH—SO₂—) compounds. The content of the alkali-soluble lowmolecular weight compound is preferably 40% by weight or less, morepreferably 30% by weight or less, and most preferably 25% by weight orless, based on the binder resin.

The compositions of the present invention are preferably used assolutions thereof in specific solvents. Such solvents may be any, aslong as they are organic solvents which sufficiently dissolve therespective solid components and can provide the solutions forminguniform coated films by methods such as spin coating. Further, they maybe used alone or as a mixture of two or more of them. Specific examplesthereof include but are not limited to n-propyl alcohol, isopropylalcohol, n-butyl alcohol, t-butyl alcohol, methyl cellosolve acetate,ethyl cellosolve acetate, propylene glycol monoethyl ether acetate,methyl lactate, ethyl lactate, 2-methoxybutyl acetate, 2-ethoxyethylacetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate,ethyl 3-methoxypropionate, N-methyl-2-pyrrolidinone, cyclohexanone,cyclopentanone, cyclohexanol, methyl ethyl ketone, 1,4-dioxane, ethyleneglycol monomethyl ether, ethylene glycol monomethyl ether acetate,ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether,diethylene glycol monomethyl ether, diethylene glycol dimethyl ether and2-heptanone.

The positive type photoresist compositions of the present invention mayfurther contain other components such as surfactants, pigments,stabilizers, coating improvers and dyes, if necessary.

Such positive type photoresist compositions of the present invention areapplied onto substrates to form thin films. The thickness of the coatedfilms is preferably 0.4 μm to 1.5 μm. As exposure means, ones in whichthe exposure wavelength is included within the range of 170 nm to 220nm, such as ArF excimer laser stepper exposure, are preferred, and ArFexcimer laser stepper exposure is particularly preferred.

The present invention will hereinafter be described in more detail byreference to examples. However, the present invention is not limitedthereto.

SYNTHESIS EXAMPLE 1 Synthesis of Monomer [II-A-2]

2-Ethylthioethanol (106 g) was dissolved in dichloromethane, and 110 gof triethylamine was added thereto, followed by cooling on an ice bath.After sufficient cooling, 105 g of methacrylyl chloride was slowly addeddropwise thereto for 1 hour. After the termination of addition, the icebath was removed, and-the temperature was spontaneously elevated to roomtemperature, followed by stirring as such for 3 hours. After thereaction was completed, acetic acid was added to the reaction product toneutralize it. Then, the resulting product was washed with distilledwater. An oil layer was concentrated and purified by silica gelchromatography to obtain 165 g of the desired monomer.

SYNTHESIS EXAMPLE 2 Synthesis of Monomer [II-C-2]

Light Ester HO-MS manufactured by Kyoeisha Chemical Co., Ltd. wasconverted to an acid chloride with thionyl chloride, and the desiredmonomer was obtained in the same manner as with synthesis example 1described above with the exception that the resulting acid chloride wasused in place of methacrylyl chloride in Synthesis Example 1.

SYNTHESIS EXAMPLE 3 Synthesis of Monomer [II-A-14]

The desired monomer was obtained in the same manner as with synthesisexample 1 described above with the exception that 2-methoxyethanol wasused in place of 2-ethylthioethanol in Synthesis Example 1.

SYNTHESIS EXAMPLE 4 Synthesis of Resin A

Tricyclodecanyl methacrylate (11.0 g), the above-mentioned monomer[II-A-2] (5.3 g) and methacrylic acid (1.7 g) were dissolved intetrahydrofuran (THF) (40 g), and then, the resulting solution washeated to 65° C. while passing a nitrogen gas therethrough for 30minutes. As a polymerization initiator, 50 mg of V-65 manufactured byWako Pure Chemical Industries, Ltd. was added thereto in 5 parts atintervals of 1 hour. After the final addition of the initiator, heatingwas continued as such for 4 hours. After the termination of heating, thetemperature of the reaction solution was lowered to room temperature.The reaction solution diluted with 50 g of THF was reprecipitated with 3liters of distilled water, thus recovering the desired copolymer as awhite powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 47,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 5 Synthesis of Resin B

Tricyclodecanyl methacrylate (11.0 g), the above-mentioned monomer[II-C-2] (9.5 g) and methacrylic acid (1.7 g) were dissolved in THF (50g), and then, the resulting solution was heated to 65° C. while passinga nitrogen gas therethrough for 30 minutes. As a polymerizationinitiator, 50 mg of V-65 manufactured by Wako Pure Chemical Industries,Ltd. was added thereto in 5 parts at intervals of 1 hour. After thefinal addition of the initiator, heating was continued as such for 4hours. After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 50 g of THF was reprecipitated with 3 liters of distilled water,thus recovering the desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 43,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 6 Synthesis of Resin C

Tricyclodecanyl methacrylate (11.0 g), the above-mentioned monomer[II-A-14] (4.8 g) and methacrylic acid (1.7 g) were dissolved in THF (40g), and then, the resulting solution was heated to 65° C. while passinga nitrogen gas therethrough for 30 minutes. As a polymerizationinitiator, 50 mg of V-65 manufactured by Wako Pure Chemical Industries,Ltd. was added thereto in 5 parts at intervals of 1 hour. After thefinal addition of the initiator, heating was continued as such for 4hours. After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 50 g of THF was reprecipitated with 3 liters of distilled water,thus recovering the desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 46,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 7

Monomer [d] having the following structure was synthesized in accordancewith the method described in JP-A-8-259626, and binder resin Dapplicable to the present invention was synthesized.

Tricyclodecanyl methacrylate (6.6 g), the above-mentioned monomer[II-A-2] (4.3 g) and monomer [d] (8.3 g) were dissolved in THF (45 g),and then, the resulting solution was heated to 65° C. while passing anitrogen gas therethrough for 30 minutes. As a polymerization initiator,50 mg of V-65 manufactured by Wako Pure Chemical Industries, Ltd. wasadded thereto in 5 parts at intervals of 1 hour. After the finaladdition of the initiator, heating was continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 50 g of THF was reprecipitated with 3 liters of distilled water,thus recovering the desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 44,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 8 Synthesis of Resin E for Comparison

Tricyclodecanyl methacrylate (11.0 g), t-butyl methacrylate (4.3 g) andmethacrylic acid (1.7 g) were dissolved in THF (40 g), and then, theresulting solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 50 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating was continued as such for 4 hours. After thetermination of heating, the temperature of the reaction solution waslowered to room temperature. The reaction solution diluted with 50 g ofTHF was reprecipitated with 3 liters of distilled water, thus recoveringthe desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 48,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 9 Synthesis of Resin F for Comparison

Tricyclodecanyl methacrylate (11.0 g), tetrahydrofuranyl methacrylate(5.2 g) and methacrylic acid (1.7 g) were dissolved in THF (42 g), andthen, the resulting solution was heated to 65° C. while passing anitrogen gas therethrough for 30 minutes. As a polymerization initiator,50 mg of V-65 manufactured by Wako Pure Chemical Industries, Ltd. wasadded thereto in 5 parts at intervals of 1 hour. After the finaladdition of the initiator, heating was continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 50 g of THF was reprecipitated with 3 liters of distilled water,thus recovering the desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 47,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 10 Synthesis of Resin G for Comparison

Tricyclodecanyl methacrylate (11.0 g), 3-oxocyclohexyl methacrylate (5.6g) and methacrylic acid (1.7 g) were dissolved in THF (43 g), and then,the resulting solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 50 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating was continued as such for 4 hours. After thetermination of heating, the temperature of the reaction solution waslowered to room temperature. The reaction solution diluted with 50 g ofTHF was reprecipitated with 3 liters of distilled water, thus recoveringthe desired copolymer as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 48,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 11 Synthesis of Photo Acid Generator (1)

Sodium hydroxide (8 g) and hydroxylamine hydrochloride (14 g) weredissolved in 200 ml of distilled water, and 25 g of dimethylmaleicanhydride added thereto. Then, the resulting solution was stirred atroom temperature for 5 hours, followed by heat stirring at 100° C. for 3hours. After the reaction was completed, aqueous hydrochloric acid wasadded to the reaction solution. Then, the resulting solution was furthersaturated with sodium chloride, and thereafter extracted with ethylacetate. The procedure of concentrating the extracted ethyl acetatesolution to one third, adding toluene to the concentrated solution andreconcentrating the solution to which toluene was added was repeated toisolate 15 g of N-hydroxymaleinimide.

In dichloromethane, 4.2 g of N-hydroxymaleinimide thus synthesized wasdissolved, and 8.5 g of trifluoromethane-sulfonic acid anhydride wasadded dropwise on an ice bath for 1 hour. After 2.8 g of pyridine wasfurther added dropwise for 2 hours, the ice bath was removed, and thetemperature was elevated to room temperature, followed by stirring assuch for 10 hours. After the reaction was completed, the reactionsolution was washed with distilled water, and concentrated to conductcrystallization in hexane. The hexane layer was concentrated to obtain10 g of the desired compound.

The following structure was confirmed by ¹³CNMR:

Examples 1 to 4 and Comparative Examples 1 to 3

In 2-heptanone, 1.2 g of each of resins A to G synthesized in SynthesisExamples described above and 0.1 g of photo acid generator (1) weredissolved so as to give a solid content of 14% by weight, and then, theresulting solution was filtered through a 0.1-μm microfilter to preparea positive type photoresist composition solution. The formulationthereof is shown in Table 1 described below.

(Evaluation Tests)

The resulting positive type photoresist composition solution was appliedonto a silicon wafer with a spin coater, and dried at 120° C. for 90seconds to prepare a positive type photoresist film-having a thicknessof about 0.5 μm, which was exposed to an ArF excimer laser beam (193nm). After exposure, heat treatment was carried out at 110° C. for 90seconds. Then, the photoresist film was developed with a 2.38% aqueoussolution of tetramethylammonium hydroxide, and rinsed with distilledwater to obtain a resist pattern profile.

[Relative Sensitivity]

Taking as a sensitivity an exposure which could reproduce a patternhaving a width of 0.5 μm, and taking the resist sensitivity of Example 1as 1, the relative sensitivity of a resist other than that of Example 1was determined by the following equation:

Sensitivity other than that of Example 1/Sensitivity of Example 1

[Aging Storage Stability]

Coefficient of Variation in Sensitivity: The coefficient of variation insensitivity was evaluated from the viewpoint of aging stability. Asolution of the positive type photoresist composition prepared wasstored at 30° C. for 1 month. Then, it was applied onto a silicon waferand exposed in the same manner as above. The relative sensitivity wasdetermined, and the difference from the above-mentioned relativesensitivity before storage was determined as the coefficient ofvariation with time.

Coefficient of Variation in Film Thickness Loss: The coefficient ofvariation in membrane decrease was evaluated from the viewpoint of agingstability. A profile of an unexposed area was observed under a scanningelectron microscope (SEM), and the thickness of the film afterdevelopment was measured. The change in the thickness of the film beforeand after development was compared between the positive type photoresistbefore storage at 30° C. for 1 month and that after storage for 1 monthto examine the coefficient of variation with time in film thicknessloss. Results thereof are shown in Table 1.

TABLE 1 Results of Resist Evaluation Coefficient of Acid CoefficientVariation in Gene- Relative of Variation Film Thickness Resin ratorSensitivity in Sensitivity Loss Example 1 A 1 1.0 5% or less 5% or lessExample 2 B 1 0.9 5% or less 5% or less Example 3 C 1 1.2 5% or less 5%or less Example 4 D 1 1.0 5% or less 5% or less Comparative E 1 1.8 (NG)5% or less 5% or less Example 1 Comparative F 1 0.7 50% (NG) 50% (NG)Example 2 Comparative G 1 1.6 (NG) 5% or less 5% or less Example 3

Comparative Examples 1 to 3 each has a problem in any one of therelative sensitivity, the coefficient of variation in sensitivity andthe coefficient of variation in film thickness loss. On the other hand,Examples 1 to 4 relating to the positive type photoresist compositionsof the present invention are at levels satisfying all of them. That is,the positive type photoresist compositions of the present invention aresuitable for lithography using far ultraviolet rays including ArFexcimer laser exposure.

SYNTHESIS EXAMPLE 12 Synthesis of Monomer [II-A′-2]

Methacrylic acid (86 g) was dissolved in 500 ml of dichloromethane, and10 g of 4-dimethylaminopyridine was added thereto. Further, 102 g of2-hydroxy-γ-butyrolactone was gently added. The resulting solution wascooled on an ice bath, and 25 g of dicyclohexylcarbodiimide was furtherslowly added thereto. After stirring as such for 30 minutes, the icebath was removed, and the temperature was spontaneously elevated to roomtemperature, followed by stirring at room temperature for 3 hours. Afterthe reaction was completed, the precipitated powder was filtered, andthe resulting filtrate was extracted with 10% aqueous hydrochloric acid.The extract was washed with an aqueous solution of sodium bicarbonate,and further with saturated saline. The resulting oil layer wasconcentrated, and purified by silica gel column chromatography to obtain150 g of the desired monomer [II-A′-2].

SYNTHESIS EXAMPLE 13 Synthesis of Monomer [II-C′-2]

Monomer [II-C′-2] was synthesized in the same manner as with SynthesisExample 12 with the exception that Light Ester HO-MS manufactured byKyoeisha Chemical Co., Ltd. was substituted for methacrylic acid inSynthesis Example 12.

SYNTHESIS EXAMPLE 14 Synthesis of Monomer [II-F′-2]

Monomer [II-F′-2] was synthesized in the same manner as with SynthesisExample 12 with the exception that a terminal carboxylic acidmethacrylate synthesized by the reaction of 3-hydroxypropionic acid andKarenzu MOI manufactured by Showa Denko K. K. was used in place ofmethacrylic acid in Synthesis Example 12.

SYNTHESIS EXAMPLE 15 Synthesis of Monomer 1 for Comparison

A monomer having the following structure was synthesized frommevalonolactone and methacrylyl chloride in accordance with the methoddescribed in Journal of Photopolymer Science and Technology, 9 (3), 509(1996).

SYNTHESIS EXAMPLE 16 Synthesis of Resin A2

Tricyclodecanyl methacrylate (22.0 g), monomer [II-A′-2] (13.6 g) andmethacrylic acid (1.7 g) were dissolved in THF (87 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 200 g of THF was reprecipitated with a mixed solvent of 4 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinA2 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 36,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 17 Synthesis of Resin B2

Tricyclodecanyl methacrylate (22.0 g), monomer [II-C′-2] (25.1 g) andmethacrylic acid (1.7 g) were dissolved in THF (114 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 200 g of THF was reprecipitated with a mixed solvent of 4 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinB2 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 37,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 18 Synthesis of Resin C2

Tricyclodecanyl methacrylate (22.0 g), monomer [II-F′-2] (32.9 g) andmethacrylic acid (1.7 g) were dissolved in THF (133 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 200 g of THF was reprecipitated with a mixed solvent of 4 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinC2 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 39,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 19 Synthesis of Resin D2

Tricyclodecanyl methacrylate (17.6 g), monomer [II-A′-2] (10.2 g),t-butyl methacrylate (5.7 g) and methacrylic acid (1.7 g) were dissolvedin THF (82 g), and then, the reaction solution was heated to 65° C.while passing a nitrogen gas therethrough for 30 minutes. As apolymerization initiator, 150 mg of V-65 manufactured by Wako PureChemical Industries, Ltd. was added thereto in 5 parts at intervals of 1hour. After the final addition of the initiator, heating and stirringwere continued as such for 4 hours. After the termination of heating,the temperature of the reaction solution was lowered to roomtemperature. The reaction solution diluted with 200 g of THF wasreprecipitated with a mixed solvent of 4 liters of distilled water/2liters of methanol, thus recovering the desired resin D2 as a whitepowder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 35,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 20 Synthesis of Resin E2

Tricyclodecanyl methacrylate (17.6 g), monomer [II-C′-2] (18.9 g),t-butyl methacrylate (5.7 g) and methacrylic acid (1.7 g) were dissolvedin THF (102 g), and then, the reaction solution was heated to 65° C.while passing a nitrogen gas therethrough for 30 minutes. As apolymerization initiator, 150 mg of V-65 manufactured by Wako PureChemical Industries, Ltd. was added thereto in 5 parts at intervals of 1hour. After the final addition of the initiator, heating and stirringwere continued as such for 4 hours. After the termination of heating,the temperature of the reaction solution was lowered to roomtemperature. The reaction solution diluted with 200 g of THF wasreprecipitated with a mixed solvent of 4 liters of distilled water/2liters of methanol, thus recovering the desired resin E2 as a whitepowder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 37,200 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 21 Synthesis of Resin F2

Tricyclodecanyl methacrylate (17.6 g), monomer [II-F′-2] (19.8 g),t-butyl methacrylate (5.7 g) and methacrylic acid (1.7 g) were dissolvedin THF (105 g), and then, the reaction solution was heated to 65° C.while passing a nitrogen gas therethrough for 30 minutes. As apolymerization initiator, 150 mg of V-65 manufactured by Wako PureChemical Industries, Ltd. was added thereto in 5 parts at intervals of 1hour. After the final addition of the initiator, heating and stirringwere continued as such for 4 hours. After the termination of heating,the temperature of the reaction solution was lowered to roomtemperature. The reaction solution diluted with 200 g of THF wasreprecipitated with a mixed solvent of 4 liters of distilled water/2liters of methanol, thus recovering the desired resin F2 as a whitepowder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 38,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 22 Synthesis of Resin G2

Tricyclodecanyl methacrylate (22.0 g), monomer 1 for comparison (19.9 g)and methacrylic acid (1.7 g) were dissolved in THF (102 g), and then,the reaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 200 g of THF was reprecipitated with a mixed solvent of 4 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinG2 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 35,600 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 23 Synthesis of Resin H2

Tricyclodecanyl methacrylate (17.6 g), monomer 1 for comparison (12.0g), t-butyl methacrylate (5.7 g) and methacrylic acid (1.7 g) weredissolved in THF (86 g), and then, the reaction solution was heated to65° C. while passing a nitrogen gas therethrough for 30 minutes. As apolymerization initiator, 150 mg of V-65 manufactured by Wako PureChemical Industries, Ltd. was added thereto in 5 parts at intervals of 1hour. After the final addition of the initiator, heating and stirringwere continued as such for 4 hours. After the termination of heating,the temperature of the reaction solution was lowered to roomtemperature. The reaction solution diluted with 200 g of THF wasreprecipitated with a mixed solvent of 4 liters of distilled water/2liters of methanol, thus recovering the desired resin H2 as a whitepowder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 34,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 24 Synthesis of Photo Acid Generator (1)

Sodium hydroxide (8 g) and hydroxylamine hydrochloride (14 g) weredissolved in 200 ml of distilled water, and 25 g of dimethylmaleicanhydride added thereto. Then, the resulting solution was stirred atroom temperature for 5 hours, followed by heat stirring at 100° C. for 3hours. After the reaction was completed, aqueous hydrochloric acid wasadded to the reaction solution. Then, the resulting solution was furthersaturated with sodium chloride, and thereafter extracted with ethylacetate. The procedure of concentrating the extracted ethyl acetatesolution to one third, adding toluene to the concentrated solution andreconcentrating the solution to which toluene was added was repeated toisolate 15 g of N-hydroxymaleinimide.

In dichloromethane, 4.2 g of N-hydroxymaleinimide thus synthesized wasdissolved, and 8.5 g of trifluoromethane-sulfonic acid anhydride wasadded dropwise on an ice bath for 1 hour. After 2.8 g of pyridine wasfurther added dropwise for 2 hours, the ice bath was removed, and thetemperature was elevated to room temperature, followed by stirring assuch for 10 hours. After the reaction was completed, the reactionsolution was washed with distilled water, and concentrated to conductcrystallization in hexane. The hexane layer was concentrated to obtain10 g of the desired compound.

The following structure was confirmed by ¹³CNMR:

Examples 5 to 10 and Comparative Examples 4 and 5

In 2-heptanone, 1.2 g of each of resins A2 to H2 synthesized inSynthesis Examples described above and 0.25 g of photo acid generator(1) were dissolved so as to give a solid content of 14% by weight, andthen, the resulting solution was filtered through a 0.1-μm microfilterto prepare a positive type photoresist composition solution. Theformulation thereof is shown in Table 2 described below.

((Evaluation Tests)

The resulting positive type photoresist composition solution was appliedonto a silicon wafer with a spin coater, and dried at 120° C. for 90seconds to prepare a positive type photoresist film having a thicknessof about 0.5 μm, which was exposed to an ArF excimer laser beam (193nm). After exposure, heat treatment was carried out at 110° C. for 90seconds. Then, the photoresist film was developed with a 2.38% aqueoussolution of tetramethylammonium hydroxide, and rinsed with distilledwater to obtain a resist pattern profile.

[Relative Sensitivity]

Taking as a sensitivity an exposure which could reproduce a patternhaving a width of 0.5 μm, and taking the resist sensitivity of Example 5as 1, the relative sensitivity of a resist other than that of Example 5was determined by the following equation:

Sensitivity other than that of Example 5/Sensitivity of Example 5

[Pattern Profile]

The resist pattern profile obtained above was observed under a scanningelectron microscope, and one showing a rectangular form was rated as Oand one showing a T-top form as x.

[Adhesion]

Minimum Width of Remaining Thin Line: The resist pattern profileobtained above was observed under a scanning electron microscope, andthe adhesion was evaluated by the width of the thinnest remaining line.That is, higher adhesion results in remaining of a pattern having athinner line width. Conversely, a pattern poor in adhesion can notadhere to a substrate as the line width becomes thinner, resulting inseparation of the pattern.

Results thereof are shown in Table 2.

TABLE 2 Minimum Relative Width of Resin Sensiti- Pattern Remaining Usedvity Profile Thin Line Example 5 A2 1.0 ∘ 0.29 Example 6 B2 0.9 ∘ 0.30Example 7 C2 0.9 ∘ 0.31 Example 8 D2 0.6 ∘ 0.28 Example 9 E2 0.5 ∘ 0.29Example 10 F2 0.6 ∘ 0.30 Comparative G2 2.4 x 0.59 Example 4 ComparativeH2 1.7 x 0.60 Example 5

Comparative Examples 4 and 5 each has problems in the relativesensitivity, the pattern profile and the adhesion. On the other hand,Examples 5 to 10 relating to the positive type photoresist compositionsof the present invention are at levels satisfying all of them. That is,the positive type photoresist compositions of the present invention aresuitable for lithography using far ultraviolet rays including ArFexcimer laser exposure.

SYNTHESIS EXAMPLE 25 Synthesis of Monomer [I-A-1]

1-Methoxy-2-methyl-2-propanol was synthesized from1-chloro-2-methyl-2-propanol and sodium methoxide.

Then, 72 g of acrylic acid was dissolved in 500 ml of dichloromethane,and 10 g of 4-dimethylaminopyridine was added thereto. Further, 90 g of1-methoxy-2-methyl-2-propanol was gently added. The resulting solutionwas cooled on an ice bath, and 25 g of dicyclohexylcarbodiimide wasfurther slowly added thereto. After stirring as such for 30 minutes, theice bath was removed, and the temperature was spontaneously elevated toroom temperature, followed by stirring at room temperature for 3 hours.After the reaction was completed, the precipitated powder was filtered,and the resulting filtrate was extracted with 10% aqueous hydrochloricacid. The extract was washed with an aqueous solution of sodiumbicarbonate, and further with saturated saline. The resulting oil layerwas concentrated, and purified by silica gel column chromatography toobtain 125 g of the desired monomer [I-A-1].

SYNTHESIS EXAMPLE 26 Synthesis of Monomer [I-A-7]

Monomer [I-A-7] was synthesized in the same manner as with SynthesisExample 25 with the exception that methylmercaptan sodium salt was usedin place of sodium methoxide.

SYNTHESIS EXAMPLE 27 Synthesis of Monomer [I-C-1]

Monomer [I-C-1] was synthesized in the same manner as with SynthesisExample 25 with the exception that the following carboxylic acid monomerwas used in place of acrylic acid:

SYNTHESIS EXAMPLE 28 Synthesis of Monomer [I-D-1]

Monomer [I-D-1] was synthesized in the same manner as with SynthesisExample 25 with the exception that Aronix M-5600 manufactured byToagosei Chemical Industry Co., Ltd. was used in place of acrylic acid.

SYNTHESIS EXAMPLE 29 Synthesis of Monomer [I-F-2]

Monomer [I-F-2] was synthesized in the same manner as with SynthesisExample 25 with the exception that a terminal carboxylic acidmethacrylate synthesized by the reaction of 3-hydroxypropionic acid andKarenzu MOI manufactured by Showa Denko K. K. was used in place ofacrylic acid in Synthesis Example 25.

SYNTHESIS EXAMPLE 30 Synthesis of Resin A3

Tricyclodecanyl methacrylate (22.0 g), monomer [I-A-1] (12.7 g) andacrylic acid (1.4 g) were dissolved in THF (55 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinA3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 32,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 31 Synthesis of Resin B3

Tricyclodecanyl methacrylate (22.0 g), monomer [I-A-9] (13.9 g) andacrylic acid (1.4 g) were dissolved in THF (57 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinB3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 33,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 32 Synthesis of Resin C3

Tricyclodecanyl methacrylate (22.0 g), monomer [I-C-1] (24.2 g) andacrylic acid (1.4 g) were dissolved in THF (70 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 150 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinC3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 35,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 33 Synthesis of Resin D3

Tricyclodecanyl methacrylate (22.0 g), monomer [I-D-1] (20.7 g) andacrylic acid (1.4 g) were dissolved in THF (66 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 150 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinD3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 34,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 34 Synthesis of Resin E3

Tricyclodecanyl methacrylate (22.0 g), monomer [I-F-2] (26.5 g) andacrylic acid (1.4 g) were dissolved in THF (80 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 125 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 200 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/3 liters of methanol, thus recovering the desired resinE3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 32,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 35 Synthesis of Resin F3 for Comparison

Tricyclodecanyl methacrylate (22.0 g), t-butyl acrylate (10.3 g) andacrylic acid (1.4 g) were dissolved in THF (50 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinF3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 31,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 36 Synthesis of Resin G3 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer a (15.4 g)and acrylic acid (1.4 g) were dissolved in THF (58 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinG3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 32,300 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 37 Synthesis of Resin H3 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer b (11.2 g)and acrylic acid (1.4 g) were dissolved in THF (58 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinH3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 31,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 38 Synthesis of Resin I3 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer c (15.9 g)and acrylic acid (1.4 g) were dissolved in THF (60 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinI3 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 32,500 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 39 Synthesis of Photo Acid Generator (1)

Sodium hydroxide (8 g) and hydroxylamine hydrochloride (14 g) weredissolved in 200 ml of distilled water, and 25 g of dimethylmaleicanhydride added thereto. Then, the resulting solution was stirred atroom temperature for 5 hours, followed by heat stirring at 100° C. for 3hours. After the reaction was completed, aqueous hydrochloric acid wasadded to the reaction solution. Then, the resulting solution was furthersaturated with sodium chloride, and thereafter extracted with ethylacetate. The procedure of concentrating the extracted ethyl acetatesolution to one third, adding toluene to the concentrated solution andreconcentrating the solution to which toluene was added was repeated toisolate 15 g of N-hydroxymaleinimide.

In dichloromethane, 4.2 g of N-hydroxymaleinimide thus synthesized wasdissolved, and 8.5 g of trifluoromethane-sulfonic acid anhydride wasadded dropwise on an ice bath for 1 hour. After 2.8 g of pyridine wasfurther added dropwise for 2 hours, the ice bath was removed, and thetemperature was elevated to room temperature, followed by stirring assuch for 10 hours. After the reaction was completed, the reactionsolution was washed with distilled water, and concentrated to conductcrystallization in hexane. The hexane layer was concentrated to obtain10 g of the desired compound.

The following structure was confirmed by ¹³CNMR:

Examples 11 to 15 and Comparative Examples 6 to 9

In 2-heptanone, 1.2 g of each of resins A3 to I3 synthesized inSynthesis Examples described above and 0.25 g of photo acid generator(1) were dissolved so as to give a solid content of 14% by weight, andthen, the resulting solution was filtered through a 0.1-μm microfilterto prepare a positive type photoresist composition solution. Theformulation thereof is shown in Table 3 described below.

(Evaluation Tests)

The resulting positive type photoresist composition solution was appliedonto a silicon wafer with a spin coater, and dried at 120° C. for 90seconds to prepare a positive type photoresist film having a thicknessof about 0.5 μm, which was exposed to an ArF excimer laser beam (193nm). After exposure, heat treatment was carried out at 110° C. for 90seconds. Then, the photoresist film was developed with a 2.38% aqueoussolution of tetramethylammonium hydroxide, and rinsed with distilledwater to obtain a resist pattern profile.

[Relative Sensitivity]

Taking as a sensitivity an exposure which could reproduce a patternhaving a width of 0.5 μm, and taking the resist sensitivity of Example11 as 1, the relative sensitivity of a resist other than that of Example11 was determined by the following equation:

Sensitivity other than that of Example 11/Sensitivity of Example 11

[Pattern Profile]

The resist pattern profile obtained above was observed under a scanningelectron microscope, and one showing a rectangular form was rated as Oand one showing a T-top form as x.

[Adhesion]

Minimum Width of Remaining Thin Line: The resist pattern profileobtained above was observed under a scanning electron microscope, andthe adhesion was evaluated by the width of the thinnest remaining line.That is, higher adhesion results in remaining of a pattern having athinner line width. Conversely, a pattern poor in adhesion can notadhere to a substrate as the line width becomes thinner, resulting inseparation of the pattern.

Results thereof are shown in Table 3.

TABLE 3 Minimum Relative Width of Resin Sensiti- Pattern Remaining Usedvity Profile Thin Line Example 11 A3 1.0 ∘ 0.30 Example 12 B3 1.0 ∘ 0.29Example 13 C3 1.1 ∘ 0.31 Example 14 D3 0.9 ∘ 0.28 Example 15 E3 0.9 ∘0.29 Comparative F3 1.8 x 0.45 Example 6 Comparative G3 2.0 x 0.47Example 7 Comparative H3 1.9 x 0.50 Example 8 Comparative I3 1.9 x 0.48Example 9[Transmission Density]

The same composition as that of the positive type photoresistcomposition solution applied onto the silicon wafer for theabove-mentioned tests was applied onto a silica plate having nophotoabsorption in the far ultraviolet region to prepare a sample fordensity measurement. The spectral adsorption in the far ultravioletregion was measured using a spectral densitometer to determine atransmission density at 193 nm, which was divided by a thickness of thecoated layer of the sample to determine a transmission density permicron of coated layer in thickness.

Results thereof are shown in Table 4.

TABLE 4 Resin Used Transmission Density Example 11 A3 0.10 Example 12 B30.15 Example 13 C3 0.19 Example 14 D3 0.20 Example 15 E3 0.18Comparative F3 0.15 Example 6 Comparative G3 1.10 Example 7 ComparativeH3 0.17 Example 8 Comparative I3 0.68 Example 9

Referring to Table 3, Comparative Examples 7 to 9 each has problems inthe relative sensitivity, the pattern profile and the adhesion. On theother hand, Examples 11 to 15 relating to the positive type photoresistcompositions of the present invention are at levels satisfying all ofthem. That is, the positive type photoresist compositions of the presentinvention are suitable for lithography using far ultraviolet raysincluding ArF excimer laser exposure.

On the other hand, Table 4 shows that all sample resins A3 to E3 of thepresent invention have a transmission density of 0.4 or less per micronof coated layer in thickness at 193 nm, and sufficiently low inphotoabsorption to exposure for patterning compared with the samples forcomparison. This means that light reaches the substrate side of acomposition layer by irradiation without significant attenuation, and isreflected in the good pattern profile and the high relative sensitivityshown in Table 3. In Comparative Examples 6 and 9, the resins low intransmission density are used, but is nevertheless inferior to thesamples of the present invention in the photoresist characteristicsshown in Table 3. This means that being low in transmission density is anecessary condition which the characteristics of the photoresists forfar ultraviolet rays should possess, but not a sufficient condition.

SYNTHESIS EXAMPLE 40 Synthesis of Monomer [I-A′-1]

Acrylic acid (72 g) was dissolved in 500 ml of dichloromethane, and 10 gof 4-dimethylaminopyridine was added thereto. Further,1-chloro-2-methyl-2-propanol was gently added. The resulting solutionwas cooled on an ice bath, and 25 g of dicyclohexylcarbodiimide wasfurther slowly added thereto. After stirring as such for 30 minutes, theice bath was removed, and the temperature was spontaneously elevated toroom temperature, followed by stirring at room temperature for 3 hours.After the reaction was completed, the precipitated powder was filtered,and the resulting filtrate was extracted with 10% aqueous hydrochloricacid. The extract was washed with an aqueous solution of sodiumbicarbonate, and further with saturated saline. The resulting oil layerwas concentrated, and purified by silica gel column chromatography toobtain 145 g of the desired monomer [I-A′-1].

SYNTHESIS EXAMPLE 41 Synthesis of Monomer [I-C′-1]

Monomer [I-C′-1] was synthesized in the same manner as with SynthesisExample 40 with the exception that the following carboxylic acid monomerwas used in place of acrylic acid:

SYNTHESIS EXAMPLE 42 Synthesis of Monomer [I-D′-1]

Monomer [I-D′-1] was synthesized in the same manner as with SynthesisExample 40 with the exception that Aronix M-5600 manufactured byToagosei Co., Ltd. was used in place of acrylic acid.

SYNTHESIS EXAMPLE 43 Synthesis of Resin A4

Tricyclodecanyl methacrylate (22.0 g), monomer [I-A′-1] (13.0 g) andacrylic acid (1.4 g) were dissolved in THF (85 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 100 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinA4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 18,000 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 44 Synthesis of Resin B4

Tricyclodecanyl methacrylate (22.0 g), monomer [I-C′-1] (24.5 g) andacrylic acid (1.4 g) were dissolved in THF (112 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 150 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/3 liters of methanol, thus recovering the desired resinB4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 19,200 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 45 Synthesis of Resin C4

Tricyclodecanyl methacrylate (22.0 g), monomer [I-D′-1] (21.1 g) andacrylic acid (1.4 g) were dissolved in THF (104 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 150 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinC4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 18,800 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 46 Synthesis of Resin D4

Tricyclodecanyl methacrylate (22.0 g), t-butyl acrylate (10.3 g) andacrylic acid (1.4 g) were dissolved in THF (80 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 2 liters ofdistilled water/2 liters of methanol, thus recovering the desired resinD4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 17,800 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 47 Synthesis of Resin E4 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer a (11.2 g)and acrylic acid (1.4 g) were dissolved in THF (90 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/3 liters of methanol, thus recovering the desired resinE4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 18,600 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 48 Synthesis of Resin F4 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer b (11.2 g)and acrylic acid (1.4 g) were dissolved in THF (90 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 100 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/3 liters of methanol, thus recovering the desired resinF4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 18,300 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 49 Synthesis of Resin G4 for Comparison

Tricyclodecanyl methacrylate (22.0 g), the following monomer c (15.9 g)and acrylic acid (1.4 g) were dissolved in THF (95 g), and then, thereaction solution was heated to 65° C. while passing a nitrogen gastherethrough for 30 minutes. As a polymerization initiator, 150 mg ofV-65 manufactured by Wako Pure Chemical Industries, Ltd. was addedthereto in 5 parts at intervals of 1 hour. After the final addition ofthe initiator, heating and stirring were continued as such for 4 hours.After the termination of heating, the temperature of the reactionsolution was lowered to room temperature. The reaction solution dilutedwith 120 g of THF was reprecipitated with a mixed solvent of 3 liters ofdistilled water/3 liters of methanol, thus recovering the desired resinG4 as a white powder.

The GPC analysis of the resulting copolymer showed that it had aweight-average molecular weight of 18,400 in terms of standardpolystyrene.

SYNTHESIS EXAMPLE 50 Synthesis of Photo Acid Generator (1)

Sodium hydroxide (8 g) and hydroxylamine hydrochloride (14 g) weredissolved in 200 ml of distilled water, and 25 g of dimethylmaleicanhydride added thereto. Then, the resulting solution was stirred atroom temperature for 5 hours, followed by heat stirring at 100° C. for 3hours. After the reaction was completed, aqueous hydrochloric acid wasadded to the reaction solution. Then, the resulting solution was furthersaturated with sodium chloride, and thereafter extracted with ethylacetate. The procedure of concentrating the extracted ethyl acetatesolution to one third, adding toluene to the concentrated solution andreconcentrating the solution to which toluene was added was repeated toisolate 15 g of N-hydroxymaleinimide.

In dichloromethane, 4.2 g of N-hydroxymaleinimide thus synthesized wasdissolved, and 8.5 g of trifluoromethane-sulfonic acid anhydride wasadded dropwise on an ice bath for 1 hour. After 2.8 g of pyridine wasfurther added dropwise for 2 hours, the ice bath was removed, and thetemperature was elevated to room temperature, followed by stirring assuch for 10 hours. After the reaction was completed, the reactionsolution was washed with distilled water, and concentrated to conductcrystallization in hexane. The hexane layer was concentrated to obtain10 g of the desired compound.

The following structure was confirmed by ¹³CNMR:

Examples 16 to 18 and Comparative Examples 10 to 13

In 2-heptanone, 1.2 g of each of resins A4 to G4 synthesized inSynthesis Examples described above and 0.25 g of photo acid generator(1) were dissolved so as to give a solid content of 14% by weight, andthen, the resulting solution was filtered through a 0.1-μm microfilterto prepare a positive type photoresist composition solution.

(Evaluation Tests)

The resulting positive type photoresist composition solution was appliedonto a silicon wafer with a spin coater, and dried at 120° C. for 90seconds to prepare a positive type photoresist film having a thicknessof about 0.5 μm, which was exposed to an ArF excimer laser beam (193nm). After exposure, heat treatment was carried out at 110° C. for 90seconds. Then, the photoresist film was developed with a 2.38% aqueoussolution of tetramethylammonium hydroxide, and rinsed with distilledwater to obtain a resist pattern profile.

[Relative Sensitivity]

Taking as a sensitivity an exposure which could reproduce a patternhaving a width of 0.5 μm, and taking the resist sensitivity of Example16 as 1, the relative sensitivity of a resist other than that of Example16 was determined by the following equation:

Sensitivity other than that of Example 16/Sensitivity of Example 16

[Pattern Profile]

The resist pattern profile obtained above was observed under a scanningelectron microscope, and one showing a rectangular form was rated as Oand one showing a T-top form as x.

[Adhesion]

Minimum Width of Remaining Thin Line: The resist pattern profileobtained above was observed under a scanning electron microscope, andthe adhesion was evaluated by the width of the thinnest remaining line.

Results thereof are shown in Table 5.

TABLE 5 Minimum Relative Width of Resin Sensiti- Pattern Remaining Usedvity Profile Thin Line Example 16 A4 1.0 ∘ 0.30 Example 17 B4 1.0 ∘ 0.29Example 18 C4 1.1 ∘ 0.31 Comparative D4 1.7 x 0.50 Example 10Comparative E4 2.1 x 0.45 Example 11 Comparative F4 1.6 x 0.48 Example12 Comparative G4 1.5 x 0.48 Example 13[Transmission Density]

The same composition as that of the positive type photoresistcomposition solution applied onto the silicon wafer for theabove-mentioned tests was applied onto a silica plate having nophotoabsorption in the far ultraviolet region to prepare a sample fordensity measurement. The spectral adsorption in the far ultravioletregion was measured using a spectral densitometer to determine atransmission density at 193 nm, which was divided by a thickness of thecoated layer of the sample to determine a transmission density permicron of coated layer in thickness.

Results thereof are shown in Table 6.

TABLE 6 Resin Used Transmission Density Example 16 A4 0.16 Example 17 B40.17 Example 18 C4 0.20 Comparative D4 0.16 Example 10 Comparative E41.10 Example 11 Comparative F4 0.17 Example 12 Comparative G4 0.68Example 13

Referring to Table 5, Comparative Examples 10 to 13 each has problems inthe relative sensitivity, the pattern profile and the adhesion. On theother hand, Examples 16 to 18 relating to the positive type photoresistcompositions of the present invention are at levels satisfying all ofthem. That is, of the resins in which the acid decomposable groups areattached by ester linkages to tertiary carbon, the resins of the presentinvention, namely resins each having the structure that tertiary carbonis substituted by a halomethylene group, are particularly suitable forlithography using far ultraviolet rays including ArF excimer laserexposure.

On the other hand, Table 6 shows that all sample resins A4 to C4 of thepresent invention have a transmission density of 0.4 or less per micronof coated layer in thickness at 193 nm, and sufficiently low inphotoabsorption to exposure for patterning compared with the samples forcomparison. This means that light reaches the substrate side of acomposition layer by irradiation without significant attenuation, and isreflected in the good pattern profile and the high relative sensitivityshown in Table 5. In Comparative Examples 10 and 13, the resins low intransmission density are used, but is nevertheless inferior to thesamples of the present invention in the photoresist characteristicsshown in Table 5. This means that being low in transmission density is anecessary condition which the characteristics of the photoresists forfar ultraviolet rays should possess, but not a sufficient condition.

As described above, according to the present invention, there can beprovided positive photoresist compositions which are sufficientlysuitable, particularly, for light in the wavelength region of 170 nm to220 nm, high in sensitivity, excellent in adhesion and can give goodresist pattern profiles.

1. A positive photoresist composition comprising a resin which has anester group represented by the following general formula (I-2) in itsmolecule and is decomposed by action of an acid to increase solubilityof the resin in an alkali solution, and a compound generating an acid byirradiation of an active light ray or radiation:

wherein R₂₁ to R₂₄, which may be the same or different, each representsa hydrogen atom or an alkyl group; and m represents 1 or 2; wherein saidresin further contains (1) repeating structure units each having analicyclic hydrocarbon moiety and further contains (2) repeatingstructure units each having a group which is decomposed by action of anacid to increase solubility of the resin in an alkali developingsolution.
 2. The positive photoresist composition according to claim 1,wherein said resin is a resin which contains repeating structure unitscorresponding to a monomer represented by the following general formula(II-2) and is decomposed by action of an acid to increase solubility ofthe resin in an alkali solution:

wherein R₂₁ to R₂₄ and m have the same meanings as given in claim 1; R₂₅represents a hydrogen atom or a methyl group; and A₂₁ represents onegroup selected from the group consisting of a single bond, an alkylenegroup, a substituted alkylene group, an ether group, a thioether group,a carbonyl group, an ester group, an amido group, a sulfonamide group, aurethane group and a urea group, or a combination of two or more ofthem.